Biden, however, stopped short of calling the killings genocide.

“We have to continue to provide Ukraine with the weapons they need to continue the fight. And we have to gather all the detail so this can be an actual – have a war crimes trial,” he said.

03:11

Russian troops accused of war crimes after mass graves found in Bucha near Ukrainian capital

Russian troops accused of war crimes after mass graves found in Bucha near Ukrainian capital

The bodies of 410 civilians have been removed from Kyiv-area towns that were recently retaken from Russian forces, Ukraine’s prosecutor-general, Iryna Venediktova, said.

Taras Shapravskyi, deputy mayor of Bucha, which is around 40km (25 miles) northwest of Kyiv, said 50 bodies were the victims of extrajudicial killings carried out by Russian troops. Purported mass graves filled with what appeared to be corpses in body bags were also photographed in Bucha.

Associated Press journalists saw 21 bodies in Bucha. One group of nine in civilian clothes were scattered around a site residents said Russian troops used as a base. They appeared to have been shot at close range. At least two had their hands tied behind their backs.

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Reuters reporters saw one man sprawled by the roadside, his hands tied behind his back and a bullet wound to his head, although Reuters could not independently verify Ukraine’s numbers or who was responsible for the killings.

Moscow said the killings were “staged” to sully Russia’s name.

The atrocities were also set to overshadow peace talks between Russia and Ukraine due to restart by video link on Monday.

Asked whether Putin would be held accountable for the civilian killings, Zelensky said others also shared the blame.

“I think all the military commanders, everyone who gave instructions and orders should be punished,” he told the CBS Face the Nation news programme.

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Poland’s Prime Minister Mateusz Morawiecki described Russia as a “totalitarian-fascist state”, saying “the bloody massacres perpetrated by Russian soldiers deserve to be called by name: This is genocide.”

US Secretary of State Antony Blinken described the images as “a punch in the gut”, while UN Secretary-General Antonio Guterres called for an independent investigation.

“Putin and his supporters will feel the consequences,” said German Chancellor Olaf Scholz, adding that Western allies would agree on further sanctions in the coming days.

Germany’s defence minister, Christine Lambrecht, said the EU must discuss banning the import of Russian gas, a departure from Berlin’s prior resistance to that idea.

French President Emmanuel Macron said there were very “clear clues pointing to war crimes” and that new sanctions were needed, while Japan said it would consult allies on that issue. Macron said new sanctions should include oil and coal.

The UN Security Council will discuss Ukraine on Tuesday and will not meet on Monday as requested by Russia, said Britain’s mission to the United Nations, which holds the presidency of the 15-member council for April.

Russia had requested the Security Council convene on Monday to discuss what it called a “provocation by Ukrainian radicals” in Bucha after Kyiv’s accusations.

Russia has previously denied targeting civilians and has rejected allegations of war crimes in what it calls a “special military operation” aimed at demilitarising and “denazifying” Ukraine. Ukraine says it was invaded without provocation.

Human Rights Watch said it had documented “several cases of Russian military forces committing laws-of-war violations” in the Ukrainian regions of Chernihiv, Kharkiv and Kyiv.

Ukraine’s foreign minister called on the International Criminal Court to collect evidence of what he called Russian war crimes. The foreign ministers of France and Britain said their countries would support any such probe.

However, legal experts say a prosecution of Putin or other Russian leaders would face high hurdles and could take years.

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Across the country, Ukraine was preparing for what its general staff said were about 60,000 Russian reservists called in to reinforce the offensive there, while British military intelligence also said Russian troops, including mercenaries from the state-linked Wagner private military company, were moving to the east.

Reuters could not independently confirm the claims.

Shelling in the eastern city of Kharkiv killed some 50 people, local authorities said, while missiles struck near the southern port of Odesa on Sunday, with Russia saying it had destroyed an oil refinery used by the Ukrainian military. The Odesa city council said “critical infrastructure facilities” were hit.

Serhiy Gaidai, the governor of eastern Luhansk region, said Russia was building up forces to break through Ukrainian defences.

“I am urging residents to evacuate. The enemy will not stop, it will destroy everything in its path,” he said on Ukrainian television.

Ukraine says it has evacuated thousands of civilians in recent days from the port city of Mariupol, decimated from a month-long siege and bombardment.

Reuters correspondents saw convoys of armoured vehicles belonging to pro-Russia forces near Mariupol.

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Ukraine evacuated more than 2,600 people from Mariupol and the region of Luhansk on Sunday, Ukrainian Deputy Prime Minister Iryna Vereshchuk said. Ukrainian officials were in talks with Russia to allow several Red Cross buses to enter Mariupol, she added.

The Red Cross abandoned earlier attempts due to security concerns. Russia blamed the charity for the delays.

There was little sign of a breakthrough in efforts to negotiate an end to the war, although Russia’s chief negotiator, Vladimir Medinsky, said talks were due to resume on Monday via videoconference.

Additional reporting by AFP