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 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. 

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"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."

The president added that Putin "should be held accountable," and said the United States needs to "get all the detail so this can be an actual war crime trial."

"This guy is brutal," Biden said. "What is happening in Bucha is outrageous and everyone has seen it – I think it is a war crime."

When asked about additional sanctions, Biden said he is "seeking more sanctions" against Russia and is "going to continue to add sanctions."

Over the weekend, Ukrainian President Volodymyr Zelenskyy, in an interview with CBS’ "Face the Nation" on Sunday, said the attacks amounted to a genocide

"We are citizens of Ukraine, and we don’t want to be subdued to the policy of [Russia]," he said. "This is the reason we are being destroyed and exterminated. And this is happening in the Europe of the 21st century. So, this is the torture of the whole nation." 

When asked Monday if he agreed with Zelenskyy's characterization of a "genocide," Biden replied: "No, I think it is a war crime."

Genocide is a type of war crime under international law.

The president’s comments come after residents of Bucha have given harrowing accounts of how Russian troops shot and killed civilians without any apparent reason. 

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

WARNING: GRAPHIC IMAGES

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A body of a person with hands bound by white cloth, who, according to residents, was shot by Russian soldiers, lies in the street in Bucha, Ukraine, on Sunday. (Reuters/Zohra Bensemra)

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." 

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Human Rights Watch has documented evidence of summary executions, unlawful violence and threats against civilians, and repeated rapes between Feb. 27 and March 14. A report from the organization also implicates Russian soldiers in looting civilian property, including food, clothing and firewood. 

Per international humanitarian law, belligerent armed forces are responsible for war crimes if they are found to have committed the willful killing, rape, torture or other inhuman type of treatment of captured civilians and combatants who are in custody.

Russian troops had rolled into Bucha in the early days of the invasion and stayed until March 30. 

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Bodies lie in a mass grave in Bucha, on the outskirts of Kyiv, Ukraine, on Sunday. (AP/Rodrigo Abd)

Russia is denying anything to do with the widespread killing of Ukrainian civilians, with Kremlin spokesman Dmitry Peskov saying Monday that "we categorically reject the accusations." 

Russia's Defense Ministry claimed in a statement that fresh photos and videos of the dead bodies "have been stage managed by the Kyiv regime for the Western media." 

Meanwhile, on Monday, U.S. Ambassador to the United Nations Linda Thomas-Greenfield announced 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.

GRAPHIC IMAGE WARNING: A dog lays next to the body of a civilian in Bucha, Ukraine, on Sunday. 

GRAPHIC IMAGE WARNING: A dog lays next to the body of a civilian in Bucha, Ukraine, on Sunday.  (Reuters/Stringer TPX Images of the Day)

"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."

Biden first called Putin a war criminal and a "murderous dictator" last month.

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Secretary of State Antony Blinken also has said he agrees that war crimes are being committed in Ukraine.

The Senate, last month, approved a resolution that will investigate Putin for war crimes, and Blinken said U.S. findings will be used to help international efforts to hold the Kremlin accountable. 

Since the onslaught of the war on Feb. 24, Russian forces have hit apartment buildings, children’s and maternity hospitals, bread lines and most recently a theater that was sheltering roughly 1,000 men, women and children in the besieged city of Mariupol.

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Russian forces have also been accused of using cluster munitions and vacuum bombs in the war, which violate international law when used indiscriminately against civilians. 

At least 1,400 civilians have been killed since Russia invaded Ukraine on Feb. 24, but the United Nations says the actual number is likely much higher. 

The International Criminal Court said earlier this month that it is opening an investigation into potential war crimes by Putin in his invasion of Ukraine. 

Fox News' Gillian Turner, Greg Norman, Bradford Betz, and The Associated Press contributed to this report.