Ukraine's deputy prime minister Iryna Vereshchuk told CNN on Monday that 11 Ukrainian mayors remain in captivity by Russian forces and that Putin's atrocities are only beginning unless he is stopped.

“This is absolutely true," Vereshchuk told CNN anchor Erin Burnett regarding the captive mayors. "We know that all of the city mayors, they are in captivity, they're being held hostage by Russians, they are unfortunately are not giving them back to us.”

“Unfortunately, so far, we have not been able to get in touch, or to free any other city mayors, and we don't even know, we think that some of them were killed," she continued.

“If we do not stop Putin today, together, this is only the beginning of those atrocities that we will reveal later on. Because as we are talking now with you, there are ... more than 100,000 civilians, women, children, elderly, who are dying in the city of Mariupol at the moment,” Vereshchuk further said.

“People are dying, they are dying of hunger, thirst, severe wounds, airstrikes, thousands of them are being killed. It is a genocide, against the Ukrainian civilians. And Putin, he realizes that he cannot stop the Ukrainian army, and that’s why he has another tactic. He is torturing and raping Ukrainian civilians, women, and this is what's his so-called second army is doing. They are fighting against the civilians, and we seem to just be watching powerless against them.”

The bodies of the mayor of a Ukrainian village outside Kyiv and her husband and adult son were reportedly found in a shallow grave Monday after the three were abducted by Russian occupying forces.

Ukrainian President Volodymyr Zelenskyy is slated to address the United Nations (UN) Security Council meeting Tuesday about the latest alleged atrocities by Russian forces against his nation.

The official Twitter account of the United Kingdom's delegation to the UN announced the upcoming speech, tweeting, "The UK Presidency of the Council will ensure the truth is heard about Russia’s war crimes. We will expose Putin’s war for what it really is."

The announcement comes after Zelenskyy visited Bucha, where Russian forces allegedly left the dead bodies of civilians in the streets, according to satellite imagery.

Ukrainian officials said the bodies of 410 civilians were found in Kyiv-area towns and cities that were recently retaken from Russian forces. In Bucha, more than 100 civilians were found buried in mass graves.

French President Emmanuel Macron speaks during an election campaign event in Paris, France, on April 2, 2022. (Benjamin Girette/Bloomberg via Getty Images)

France is expelling "many" Russian diplomats following a massacre in the Ukrainian town of Bucha.

"France has decided this evening to expel many Russian personnel posted in France under diplomatic status, whose activities are counter to our security interests," read a Monday statement from the Ministry for Europe and Foreign Affairs.

"This action is part of a European movement. Our first responsibility is always to ensure the security of French and European citizens," the statement continued.

Approximately 35 diplomats will be expelled from the country following the announcement, according to Agence France-Presse.

Earlier on Monday, French President Emmanuel Macron called for additional sanctions on Russia, according to a report. White House national security adviser Jake Sullivan later announced that the U.S. will be working with its allies to impose further sanctions.

White House national security adviser Jake Sullivan told reporters Monday that the United States is planning to announce further sanctions against Russia in the wake of actions President Biden has characterized as "a war crime."

“You can expect further sanctions announcements this week. And we are coordinating with our allies and partners on what the exact parameters of that will be, but yes, this week we will have additional economic pressure elements to announce,” Sullivan said.

Sullivan echoed the president by describing Russian forces' alleged actions in Bucha, Ukraine, as a war crime, but said they were not ready to call it "genocide."

"We have seen atrocities, we have seen war crimes," he said, but added they "have not seen a level of systemic depravation of life” that could be defined as a genocide.

White House national security adviser Jake Sullivan said Monday during a press briefing that Russia is guilty of war crimes and that the photos emerging from Bucha seem to be further evidence.

"We had already concluded that Russia committed war crimes in Ukraine, and the information from Bucha appears to show further evidence of war crimes," Sullivan said. He also claimed the U.S. presently believes Russia is "revising its war aims."

"Russia is repositioning its forces to concentrate its offensive operations in eastern and parts of southern Ukraine, rather than target most of the territory," he said.

Earlier on Monday, President Biden condemned Russian President Vladimir Putin as a "war criminal."

Ukrainian officials said the bodies of 410 civilians were found in Kyiv-area towns and cities that were recently retaken from Russian forces. In Bucha, more than 100 civilians were found buried in mass graves.

A convoy of seven buses with the International Committee of the Red Cross (ICRC) intended to evacuate people from Mariupol, Ukraine, was reportedly stopped Monday on the way to its destination and is being held by police in nearby Manhush.

"A team from the International Committee of the Red Cross (ICRC) is being held in the town of Manhush, 20 kilometers west of Mariupol," ICRC spokesperson Jason Straziuso said, according to Reuters. He said police were holding the convoy but clarified that it was "not a hostage situation."

The bodies of the mayor of a Ukrainian village outside Kyiv and her husband and adult son were reportedly found in a shallow grave after the three were abducted by Russian occupying forces.

Mayor of the Village of Motyzhyn, Olga Sukhenko, was "unfortunately killed in captivity by the Russians," Ukrainian Deputy Prime Minister Iryna Vereshchuk confirmed.

"This is a war crime," Vereshchuk said in an address of Sukhenko’s killing. "The guilty will inevitably be punished in accordance with international humanitarian law."

Vereshchuk said there are 11 mayors and community heads in Russian captivity across Ukraine, including leaders from Kyiv, Kherson, Kharkiv, Zaporizhzhia, Mykolaiv and Donetsk regions.

Fox News' Danielle Wallace contributed to this report.

For more on this story: Ukraine mayor, family kidnapped by Russian forces found dead, tortured in shallow grave: Ukrainian officials

Tanya Nedashkivs'ka, 57, mourns the death of her husband, killed in Bucha, on the outskirts of Kyiv, Ukraine, on Monday. (AP/Rodrigo Abd)

World leaders are reacting with outrage Monday as evidence is emerging of what appears to be deliberate killings of Ukrainian civilians by the Russian military in cities like Bucha. 

Ukrainian President Volodymyr Zelenskyy, who visited Bucha Monday, described the grisly acts as "war crimes" that "will be recognized by the world as genocide."  

Russia, meanwhile, is continuing to claim its military had nothing to do with deaths of the civilians, some of which were recently found dead with their wrists bound and with bullet wounds in their head.  

Here is how the world is reacting to the massacre in Bucha and the discovery of what Ukraine says is the bodies of 410 civilians in towns around the capital, Kyiv, that were recaptured from Russian forces in recent days.

For more on this story: World leaders react to Bucha, Ukraine massacre: ‘Genocide’, ‘Despicable’, ‘Dreadful’

A senior U.S. defense official said Monday that the U.S. has coordinated the transfer of security aid packages from half a dozen countries to Ukraine over the last 24 hours as Russia is continuing its invasion.

"Everything we're doing in respect to Ukraine is being expedited. Everything," the official said.

When asked about civilian killings in Bucha, the official said "It's sickening, it's disgusting" and that the U.S. believes it "should be added to the allegations of war crimes and investigated."

The official also said two-thirds of Russian troops north of Kyiv have now moved away from the area or into Belarus.

Fox News' Liz Friden contributed to this report.

Ukrainian President Volodymyr Zelenskyy examines the site of a recent battle in Bucha, close to Kyiv, Ukraine, on Monday. (AP/Efrem Lukatsky)

Appearing somber and at times visibly emotional, Ukrainian President Volodymyr Zelenskyy paid a visit to the town of Bucha outside of the capital of Kyiv Monday after disturbing images surfaced showing the bodies of civilians tortured and killed after Russian troops pulled back in recent days.

“First of all, it’s very important to us that the press is here and there are journalists,” Zelenskyy told reporters in Bucha on Monday. “We want you to show the world what was happening here, what the Russian military was doing, what the Russian regime was doing.”

Ukraine’s Prosecutor General Iryna Venedyktova said Sunday that the bodies of 410 civilians have been retrieved from Bucha, the neighboring towns of Irpin and Hostomel and smaller villages around Kyiv.

For more on this story: Ukraine's Zelenskyy visits Bucha massacre site: 'War crimes' must be recognized by the world as 'genocide'

Russian President Vladimir Putin chairs a Security Council meeting on Friday. (Mikhail Klimentyev, Sputnik, Kremlin Pool Photo via AP)

President Biden on Monday called for an "actual war crime trial" as evidence of atrocities committed against Ukrainian civilians in Bucha emerged over the weekend, but denied that the attacks amounted to a "genocide," while, again, labeling Russian President Vladimir Putin as a "war criminal."

Ukrainian officials said the bodies of 410 civilians were found in Kyiv-area towns and cities that were recently retaken from Russian forces. In Bucha, alone, more than 100 civilians were found buried in mass graves.

"He is a war criminal," Biden said of Putin Monday morning upon returning to Washington D.C., vowing that the United States will "continue to provide Ukraine with weapons they need to continue to fight."

For more on this story: Biden calls for Ukraine war crimes trial, denies 'genocide' in Bucha

The United Nations on Monday confirmed over 3,500 people killed or wounded since the start of the Russian invasion of Ukraine on Feb. 24.

That number is likely just the tip of the iceberg as the group has been unable to gain access to areas of heavy fighting.

The U.N. Office of the High Commissioner for Human Rights (OHCHR) officially confirmed that 1,430 civilians had been killed and 2,097 injured since the Russian invasion began, with 121 children among the dead. The office said explosive weapons – heavy artillery, missile and airstrikes – caused most deaths.

The OHCHR has cautioned that this likely was only the beginning. Intense hostilities in areas across the country, especially in the Eastern regions of Donestsk and Luhansk, have prevented independent confirmation. Corroboration is being sought in Mariupol, Izium, Popsana and Irpin.

For more on this story: UN: Russia's Ukraine war sees at least 1,430 civilians killed, numbers expected to rise significantly

GRAPHIC IMAGE WARNING: A man lifts a door covering the opening of an underground concrete enclosure in Bucha where bodies of civilians killed by Russian forces, according to residents, are dumped as people were unable to transport them to a cemetery. (AP/Vadim Ghirda)

Russia is facing a rapidly escalating international outcry as more horrific images and stories are emerging of alleged atrocities being committed against Ukrainian civilians.

One Ukrainian lawmaker said that Russian troops beheaded an elderly woman who was trying to flee the city of Bucha, where bodies have been found in mass graves. 

Ukrainian parliament member Oleksiy Goncharenko said Russian troops beheaded an elderly woman who was trying to flee the city of Bucha, where bodies have been found in mass graves, describing the graphic scene in the Kyiv region as a "scene from a horror movie." 

"That's a real genocide. Russians should pay for these war crimes," Goncharenko said Monday outside the vehicle where the grandmother allegedly was traveling in with her daughter and granddaughter before her gruesome death, according to Reuters.

Ukrainian officials say the bodies of 410 civilians were found in Kyiv-area towns and cities – like Bucha – that were recently retaken from Russian forces. 

For more on this story: Bucha massacre: Global outcry against Russia escalates as horrifying stories emerge of Ukraine atrocities

The leader of the British secret intelligence agency, MI6, said Sunday that "we knew" that Russian President Vladimir Putin’s invasion plans for Ukraine included "summary executions." 

The shocking assertion appears to tie Putin directly to what Western countries have decried as war crimes coming to light in the suburbs of Kyiv as Russian troops have pulled back in recent days. 

Ukrainian officials and at least the leaders of Poland and Spain have gone a step further to say Russians committed genocide during what's been deemed the Bucha massacre, as shocking images have surfaced of civilians with their hands tied behind their backs shot and killed at close range and bodies of women and children showing signs of rape and torture. 

"We knew Putin’s invasion plans included summary executions by his military and intelligence services," Chief of MI6 Richard Moore tweeted on Sunday. "The reports of execution-style killings of civilians emerging from liberated areas are horrifying and chilling."  

For more on this story: MI6 chief says 'summary executions' seen in Bucha, Ukraine, were part of Putin's invasion plan

UN High Commissioner for Human Rights Michelle Bachelet said Monday that it is "vital that all efforts are made to ensure there are independent and effective investigations into what happened in Bucha to ensure truth, justice and accountability, as well as reparations and remedy for victims and their families."

She added that she is "horrified by the images of civilians lying dead on the streets and in improvised graves in the town of Bucha in Ukraine."

"Reports emerging from this and other areas raise serious and disturbing questions about possible war crimes, grave breaches of international humanitarian law and serious violations of international human rights law," Bachelet also said.

Soldiers walk amid destroyed Russian tanks in Bucha, on the outskirts of Kyiv, on Sunday. (AP/Rodrigo Abd)

European leaders are speaking out as evidence is emerging of Ukrainian civilians being killed by Russia's military. Here is what they are saying:

- Prime Minister Boris Johnson’s spokesman, Max Blain, said bodies found in areas recently recaptured from Russia showed “despicable attacks against innocent civilians, and they are yet more evidence that Putin and his army are committing what appear to be war crimes in Ukraine.”

- Albanian Prime Minister Edi Rama said in a tweet that the "dreadful images of civilians killed in Bucha Massacre, Ukraine, by the Russian army are shocking. "Everything must be done for an independent investigation of such horrible crimes," he added. "Nothing can ever excuse such cruelty. What a pain and what a shame!"

- Kosovo’s Prime Minister Albin Kurti said the bodies found in Bucha reminded him of similar atrocities committed in his country during the 1998-1999 war between ethnic Albanian independent fighters and Serbian forces. “Mass graves, people brutally killed with body parts missing, burned houses and cities turned to rubble are all familiar scenes from genocidal regimes,” he posted Monday on Twitter.

- Poland Prime Minister Mateusz Morawiecki said Monday that "Russia is already a totalitarian-fascist state today."“The bloody massacres perpetrated by Russian soldiers deserve to be called by name: This is genocide and this crime must be tried as the crime of genocide,” he added.

The Associated Press contributed to this report.

Russian Ambassador to the United Nations Vasily Nebenzya speaks during an emergency meeting of the General Assembly at United Nations headquarters on March 24. (AP/Seth Wenig)

U.S. Ambassador to the United Nations Linda Thomas-Greenfield announced Monday that the U.S. will ask U.N. members to suspend Russia from the Human Rights Council as its invasion of Ukraine continues.

With a two-thirds majority vote, the 193-member U.N. General Assembly can suspend Russia's membership for committing violations of human rights, according to Reuters.

"Russia's participation on the Human Rights Council is a farce," Thomas-Greenfield reportedly said Monday, adding that "it is wrong, which is why we believe it is time the U.N. General Assembly vote to remove them."

Russian President Vladimir Putin on Monday has signed an order making it harder for residents of countries that Moscow deems "unfriendly" to get a visa, according to Reuters.

The order -- in response to sanctions levied against Moscow -- suspends Russia's simplified visa issuance program with some European Union countries as well as Norway, Switzerland, Denmark and Iceland, the news agency reports.

Kira Rudik, a Ukrainian parliament member, discusses the 'terrible deaths' she has witnessed during Russia's invasion of Ukraine.

Current Russian military activity in Ukraine. (Fox News)

The United Kingdom's Ministry of Defence said Monday that "Russian troops, including mercenaries from the Russian state-linked Wagner private military company, are being moved" into eastern Ukraine.

"Russian forces are continuing to consolidate and reorganize as they refocus their offensive into the Donbas region in the east of Ukraine," it added in a tweet.

Pope Francis arrives in his popemobile at the Granaries Square in Floriana, Malta, Sunday, April 3, 2022, to celebrate a mass. Pope Francis opened his second and final day in Malta by visiting the Grotto of St. Paul in Rabat, where the disciple stayed after being shipwrecked en route to Rome in AD 60. (AP Photo/Andrew Medichini)

Pope Francis called the ongoing invasion of Russian forces in Ukraine a “sacrilegious” war, during a prayer Sunday where he also called for its ending.

“May we be tireless in praying and in offering assistance to those who suffer,” the Vatican said from Malta.

Pope Francis later told a group of reporters he had no immediate plan to visit Kyiv but such a visit was “on the table.”

The Pope also recognized reporters who have died or were injured covering the news in Ukraine.

“I want to offer condolences for your colleagues who have fallen, no matter what side, I don’t care," he said. "Your work is a work for the common good. They died in service of the common good: information. We wont forget them. They were courageous. I pray for them, and may the Lord reward their work.”

The Associated Press contributed to this report.

NANTERRE, FRANCE - APRIL 2: French President Emmanuel Macron - candidate 'La Republique En Marche!' (LREM) for his re-election in the 2022 presidential election - during his campaign rally at Paris La Defense Arena on April 2, 2022 in Nanterre near Paris, France. (Photo by Jean Catuffe/Getty Images)

On Monday, French President Emmanuel Macron called for additional sanctions on Russia following a massacre in the Ukrainian town of Bucha, according to a report.

During an interview on France Inter radio, Macron said "very clear clues" indicate Russian forces committed egregious actions, including possible war crimes in the city, Reuters reported.

Russia has denied any wrongdoing in their attack on Bucha.

A mass grave in Bucha, on the outskirts of Kyiv, Ukraine, Sunday, April 3, 2022. Ukrainian troops are finding brutalized bodies and widespread destruction in the suburbs of Kyiv, sparking new calls for a war crimes investigation and sanctions against Russia. (AP Photo/Rodrigo Abd)

Bodies wrapped in black tarp lie in a mass grave on the outskirts of Kyiv as Ukrainian troops assess the destruction after Russian troops withdrew from the area.

In another village, the bodies of a mayor, her husband and son, and of a man believed to be a Ukrainian serviceman, also lie in a muddy pit behind a plot of land with houses where Russian forces had slept.

A lifeless body of a man with his hands tied behind his back was also discovered in what Ukrainians described as a "scene from a horror movie." 

Read more here: Ukraine war photos: Horrific findings after Russian retreat from Kyiv outskirts

Polish Prime Minister Mateusz Morawiecki during a press conference in Warsaw, Poland, on March 24, 2022 (Photo by Mateusz Wlodarczyk/NurPhoto via Getty Images)

Poland Prime Minister Mateusz Morawiecki called on the European Union to enact "sanctions which actually work" to derail Russia's economy following "acts of genocide" at the Bucha massacre.

"The massacre in Bucha is more than an alarm bell for Europe and the world," Morawiecki said in a statement.

"It is a terrible cry for justice, freedom and the right to life; for basic and universal values," he added. "The EU must confiscate all Russian assets in its western banks as well as those of Russian oligarchs. It must sever all trade relations with Russia without delay."

"European money must stop flowing to the Kremlin. Putin’s criminal and increasingly totalitarian regime needs to have one thing imposed on it: SANCTIONS WHICH ACTUALLY WORK."

Siuzanna Iglidan, a Ukrainian musician and opera singer, performed at the Grammys alongside award-winning American artist John Legend.

The duo, who sang "Free," were joined by Ukrainians singer-actress Mika Newton and poet Lyuba Yakimchuk.

The performance followed a video address by Ukrainian president Volodymyr Zelenskyy, where he encouraged people to sing and play music to "fill the silence" caused by his country's war with Russia.

“Our musicians wear body armor instead of tuxedos,” Zelenskyy said. “We are fighting Russia, which brings horrible silence with its bombs. The dead silence. Fill the silence with your music.”

"Tell the truth about the war on your social networks, on TV. Support us in any way you can any, but not silence. And then peace will come to all our cities,” the Ukrainian president added.

Ahead of her performance, Iglidan said she was "honored" to represent her country.

The Associated Press contributed to this report.

Ukrainian President Volodymyr Zelenskyy addressed the 64th annual Grammy Awards on Sunday in a pre-taped speech that emphasized the suffering on his country.

"The war. What is more opposite of music? The silence of ruined cities and killed people,” said Zelenskyy. “Our children draw swooping rockets, not shooting stars. Over 400 children have been injured and 153 children died, and we will never see them drawing. Our parents are happy to wake up in the morning in bomb shelters, but alive. Our loved ones don’t know if we will be together again. The war doesn’t let us choose who survives and who stays in eternal silence."

“Our musicians wear body armor instead of tuxedos," he continued. "They sing to the wounded in hospitals. Even to those who can’t hear them. But the music will break through anyway. We defend our freedom. To live. To love. To sound. On our land, we are fighting Russia which brings horrible silence with its bombs. Fill the silence with your music. Fill it today. Tell our story. Tell the truth about the war on your social networks and TV. But not silence."

A woman walks amid destroyed Russian tanks in Bucha, in the outskirts of Kyiv, Ukraine, Sunday, April 3, 2022. (AP Photo/Rodrigo Abd)

As Russian forces withdrew from the area around Ukraine's capital city of Kyiv, they left horrific scenes in their wake. Bodies wrapped in black tarp lay in a mass grave on the outskirts of Kyiv. In another village, the bodies of a mayor, her husband and son, and of a man believed to be a Ukrainian serviceman, also lie in a muddy pit behind a plot of land with houses where Russian forces had slept.

Zelenskyy addressed these scenes in his address in the wee hours of Monday morning.

"Presidents do not usually record addresses like this. But today I have to say just that," the president said. "After what was revealed in Bucha and our other cities the occupiers were expelled from. Hundreds of people were killed. Tortured, executed civilians. Corpses on the streets. Mined area. Even the bodies of the dead were mined!"

"The pervasive consequences of looting," he added. "Concentrated evil has come to our land. Murderers. Torturers. Rapists. Looters. Who call themselves the army. And who deserve only death after what they did."

"I want every mother of every Russian soldier to see the bodies of the killed people in Bucha, in Irpin, in Hostomel. What did they do? Why were they killed? What did the man who was riding his bicycle down the street do? Why were ordinary civilians in an ordinary peaceful city tortured to death? Why were women strangled after their earrings were ripped out of their ears? How could women be raped and killed in front of children? How could their corpses be desecrated even after death? Why did they crush the bodies of people with tanks? What did the Ukrainian city of Bucha do to your Russia? How did all this become possible?"

"Russian mothers! Even if you raised looters, how did they also become butchers? You couldn't be unaware of what's inside your children. You couldn't overlook that they are deprived of everything human. No soul. No heart. They killed deliberately and with pleasure," the president said.

Click here for Sunday's live coverage.