US President Joe Biden has called for Russian President Vladimir Putin to be tried for war crimes as evidence emerges of atrocities allegedly committed by Russian forces in Ukraine.
There is mounting international anger over the alleged killing of civilians in Bucha, a town near the capital Kyiv.
“This guy is brutal,” Mr Biden said of the Russian leader, adding that he believes Mr Putin “is a war criminal”.
Without evidence, Russia said images of atrocities had been staged by Ukraine.
US officials say they are supporting a team of international prosecutors heading to Bucha to collect evidence.
The Ukrainian government has started a war crimes investigation after it said the bodies of 410 civilians had been found in areas around Kyiv. Some were discovered in mass graves while others had their hands tied and had apparently been shot at close range.
Officials in Kyiv also accused Russian forces of killing a village head, her husband and her sonin the village of Motoyzhyn for aiding Ukrainian troops in the area.
“You may remember I got criticised for calling Putin a war criminal,” Mr Biden said. “You saw what happened in Bucha – he is a war criminal… but we have to gather all the detail so this can have a war crimes trial.”
Mr Biden said the Bucha discovery was “outrageous” and said that it is important Mr Putin is “held accountable” for atrocities committed by his military Ukraine.
He added that he intends to seek to impose further sanctions on Russia.