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US President Joe Biden called Russian President Vladimir Putin a war criminal on Monday and urged holding a war crimes trial, as a global outcry mounted over civilian killings in the Ukrainian town of Bucha.
"You saw what happened in Bucha," Mr Biden told reporters at the White House. "This warrants him - he is a war criminal."
The discovery of a mass grave and tied bodies shot at close range in Bucha, outside Kyiv, a town taken back from Russian troops, looked set to galvanise the US and Europe into additional sanctions against Moscow.
Mr Biden said: "We have to gather the information. We have to continue to provide Ukraine with the weapons they need to continue the fight. And we have to get all the detail so this can be an actual, have a war crimes trial."
Mr Putin "is brutal. And what's happening in Bucha is outrageous, and everyone's seen it," Mr Biden said.
The Kremlin categorically denied any accusations related to the murder of civilians, including in Bucha, where it said the graves and corpses had been staged by Ukraine to tarnish Russia.
Ukrainian President Volodymyr Zelenskyy spoke on national television from the town of Bucha in the Kyiv region on Monday.
"These are war crimes and will be recognised by the world as genocide," Mr Zelenskyy said, wearing body armour and surrounded by military personnel.
The persecution of war crimes could be directed through the International Criminal Court (ICC), though the US in 2002 pulled its support from the independent panel.
White House National Security Advisor Jake Sullivan also suggested other venues could be considered.
Also on Monday, Washington's UN ambassador said it would ask the UN General Assembly to suspend Russia from the Human Rights Council.
Mr Biden also told reporters that he is "seeking more sanctions" as a response.
- with Reuters.