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," Biden said of the Russian leader, adding that he believes Putin "is a war criminal".
Without evidence, Russia said images of atrocities had been staged by Ukraine.
Biden's intervention follows the publication of new satellite photos by the earth observation company Maxar, which appear to show bodies lining Bucha's streets during its occupation by Russian forces.
An analysis of the photos by the New York Times showed at least 11 bodies on the streets since 11 March, when Russian forces controlled the city.
Russia claims that no civilians suffered under the Russian occupation of Bucha and says footage and photos from the city were staged.
But the timing of these satellite images appears to disprove the idea that the bodies only appeared after Russian soldiers left.
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 son in the village of Motoyzhyn for aiding Ukrainian troops in the area.
"You may remember I got criticised for calling Putin a war criminal," 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."
Biden said the Bucha discovery was "outrageous" and said that it is important Putin is "held accountable" for atrocities committed by his military in Ukraine.
He added that he intends to seek to impose further sanctions on Russia.
