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 Nazi leaders were 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.
Russia has denied killing civilians and says the scenes of bodies in Bucha were fabricated.
Clive Myrie presents BBC News at Ten reporting by Sarah Smith in Washington and Steve Rosenberg in Moscow.
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