Vladimir Putin has been accused of genocide as horrifying footage of dead civilians lying in the street with their hands tied behind their backs emerges.
Pictures and videos of dead Ukrainian civilians in Bucha, a town abandoned by Russian forces outside Kyiv, have been seen across the world.
Ukrainian President Volodymyr Zelensky said citizens are being "exterminated" as Western leaders condemned the images.
"Indeed, this is genocide. The elimination of the whole nation and the people," Zelensky told CBS, speaking through a translator.
"We are the citizens of Ukraine and we don't want to be subdued to the policy of Russian Federation.
"This is the reason we are being destroyed and exterminated."
Zelensky's remarks came a day after Ukrainian forces moved into the town of Bucha near Kyiv and found what officials and witnesses said were the bodies civilians killed by Russian forces.
Russia's defence ministry denied the allegations, saying footage and photographs showing dead bodies in Bucha were "yet another provocation" by Kyiv.
Human Rights Watch (HRW) said on Sunday that it had found "several cases of Russian military forces committing laws-of-war violations" in Russian-controlled regions such as Chernihiv, Kharkiv, and Kyiv.
Asked whether Russian President Vladimir Putin would be held accountable, Zelensky said others also shared the blame.
"I think all the military commanders, everyone who gave instructions and orders should be punished adequately."
Asked what would constitute adequate punishment, he said: "When we find people with hands tied behind their back and decapitated ... I don't know what law or what imprisonment term would be adequate for this."
U.S. Secretary of State Antony Blinken said the images of dead Ukrainian civilians found in Bucha were a "punch in the gut" and those responsible must be held accountable.
NATO Secretary-General Jens Stoltenberg called the killings in Bucha a "brutality" unseen in Europe for decades.
Asked whether Russian forces would need to withdraw to positions before the Feb. 24 invasion, Zelensky said: "It should be 100% withdrawal of troops to the borders that existed
prior to the 24th of February, at least."
"This would make us to at least start discussing other questions about the deoccupation."
