President Joe Biden on Monday called for a war crimes trial against Russian President Vladimir Putin and more sanctions against Russia following new reports of atrocities in Ukraine after Russian troops retreated from areas around Kyiv.

“We saw what happened in Bucha. He is a war criminal,” Biden told reporters when returning to the White House from Delaware. His State Department later said the barbaric acts were not rare individual instances but rather “part of a broader, troubling campaign.”

Biden joined a growing chorus of world leaders on Monday who condemned Russia after Ukrainian officials said the bodies of 410 civilians were found in Kyiv-area towns that were recently retaken from Russian forces.

In Bucha, 280 people were buried in mass graves, according to Oleksiy Arestovych, an adviser to Ukrainian President Volodymyr Zelenskyy, who visited the city Monday. Associated Press reporters saw the bodies of at least 21 people in various spots around Bucha. Russian authorities have dismissed images of the dead civilians as fake.

ARE ATROCITIES A GAME CHANGER? Atrocities near Kyiv fuel global outrage. Will it be a tipping point in the war?

Leaders and top government officials in France, Albania, Kosovo, Spain, Poland, Estonia, Japan, New Zealand and the EU’s top diplomat condemned the actions, and the U.N. High Commissioner for Human Rights called for an investigation. France and Germany expelled several Russian diplomats.

new report from Human Rights Watch says the nonprofit has documented several cases of Russia committing “laws-of-war violations” against civilians in Ukraine. The report, released Sunday, said Russian military forces have committed war crimes in Chernihiv, Kharkiv and Kyiv, including repeated rape, two cases of summary execution and other cases of unlawful violence and threats against civilians from Feb. 27 to March 14.

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