Mikhail Klimentiev Sputnik Reuters President Joe Biden on Monday demanded that evidence be gathered to try Russian leader Vladimir Putin for war crimes related to his nation’s invasion of Ukraine. “He is a war criminal,” Biden said of Putin, following reports of mass killings of Russian civilians by Russian troops in the city of Bukha, northwest of the Ukrainian capital, Kiev. “This guy is brutal and what is happening in Bucha is outrageous and everyone has seen it,” Biden told reporters. “I think it’s a war crime … He has to be held accountable.” Biden also said he planned to impose additional sanctions on Russia for its behavior during the war, which began with an invasion on February 24. “I will inform you,” the president replied when asked by a journalist about the nature of these expected sanctions. US President Joe Biden speaks to reporters as he arrives at Fort McNair in Washington, DC on April 4, 2022. Mandel Ngan | AFP | Getty Images Ukrainian President Volodymyr Zelenskyy had earlier said that Russian forces were committing genocide, with the Ukrainian people being “destroyed and annihilated.” The mayor of Bucha said about 300 people had been killed as Chechen fighters took control of the area. Russia has denied allegations that its troops killed civilians in Bukhara. “You may remember I was criticized for calling Putin a war criminal,” Biden said Monday. “Well, the truth of the matter, you saw what happened to Bucha. That justifies him – he is a war criminal,” Biden said. “But we must gather the information. We must continue to provide Ukraine with the weapons it needs to continue the fight,” he said. “We need to know all the details so that a war crime trial can take place.”