Originally Published: 04 APR 22 11:13 ET

Updated: 04 APR 22 11:52 ET

By Allie Malloy, CNN

(CNN) -- President Joe Biden on Monday called the atrocities allegedly committed by Russian forces in Bucha, Ukraine, a "war crime" and called for a trial to take place against Russian President Vladimir Putin.

The US President did not, however, label the killings a "genocide" but said he was looking into additional sanctions against Russia.

Biden said the images coming from Bucha warranted calling Putin a "war criminal," adding, "but 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 details so this can be an actual -- have a war crime trial."

Biden's assessment that the killings did not amount to a genocide puts him at odds with that of Ukrainian President Volodymyr Zelensky, who used the term during an interview with CBS on Sunday.

"This guy (Putin) is brutal and what's happening in Bucha is outrageous and everyone's seen it," Biden said.

Images released this weekend show civilian bodies strewn across a street following the withdrawal of Russian forces, and CNN reporters observed a mass grave in the town, with residents saying they believe at least 150 people are buried there.

The scenes out of the Kyiv suburb of Bucha have drawn international outrage, with Western leaders calling for war crimes investigations and fresh sanctions against Russia.

US Secretary of State Antony Blinken said Sunday that the State Department would help document any attacks by Russian troops against Ukrainian civilians. NATO Secretary General Jens Stoltenberg called the deaths of civilians in Bucha a "brutality" and said "I strongly welcome" an investigation by International Criminal Court, which has opened an investigation into war crimes in Ukraine.

The Russian Ministry of Defense claimed the extensive footage of dead civilians in Bucha was "fake" and that "not a single local resident suffered from any violent actions" during Russia's occupation of the town. "In the settlements of the Kiev region, Russian military personnel delivered and issued 452 tons of humanitarian aid to civilians," the ministry said in a statement.

This story has been updated with additional background information.