Ukraine’s President Volodymyr Zelensky has accused the Russian military of carrying out the worst crimes since World War Two.
He told the UN security council that civilians had been murdered and Russian tanks had crushed people “for pleasure”.
He called for those responsible to be tried as Nazis wer at Nuremberg.
Gruesome images of bodies lying in the street in towns such as Bucha have generated condemnation worldwide.
After his speech by video link to the Security Council, Mr Zelensky showed a graphic video of images of dead Ukrainians, some burned and disfigured.
“The Russian military searched for and purposefully killed anyone who served our country,” he said.
“They killed entire families, adults and children, and they tried to burn the bodies.”
Satellite image of the bodies of alleged civilians in the streets in Bucha, Ukraine on 19 March
Satellite images show what appear to be the bodies of civilians in the streets of Bucha
Russian UN Ambassador Vasily Nebenzia said there was no evidence Russian troops had carried out atrocities.
“We’ve heard once again a huge amount of lies about Russian soldiers and military,” he said.
As expected, President Volodymyr Zelensky launched a ferocious, passionate attack on the Russian military for its alleged violations in Bucha and elsewhere.
The catalogue of horrors Mr Zelensky lists includes throats slashed, limbs cut off, and women raped in front of their children.
He says there’s no difference between this and the actions of terrorists, except that Russia is a member of the UN Security Council.
This is the speech of a man who feels he has the highest of moral high grounds.
Mr Zelensky said the UN had to act, because not doing so would mean there was no point to the world body.
“Are you ready to close the UN? And the time of international law is gone? If your answer is no, then you need to act immediately,” he said, adding that “accountability must be inevitable”.
“We are dealing with a state that turns its veto at the UN Security Council into the right to [cause] death,” he said.
He called for the establishment of a special international tribunal to deal with the crimes, and for Russia to be removed from the UN’s Security Council.
There was “not a single crime they would not commit”, Mr Zelensky added.
“The world has yet to see they have done in other occupied cities and regions of our country.”
UN Secretary-General António Guterres said he would “never forget” seeing images of dead civilians in Bucha.
He warned the Security Council that Russia’s invasion is one of the greatest challenges ever to the international order “because of its nature, intensity, and consequences”.
The US reiterated its call for Russia to be suspended from the UN Human Rights Council.
Linda Thomas-Greenfield, the US ambassador to the UN, told the Security Council: “Russia should not have a position of authority in a body whose very purpose is to promote respect for human rights.”
China, which has avoided criticising the Russian invasion, said that the reports of civilian deaths in Ukraine were “very disturbing”, but said any accusations should be based on verified facts.