Ukrainian President Volodymyr Zelensky has accused Russia of implementing "a bloody reconstruction of Nazism".
In a speech commemorating World War Two, he said the Russian army was replicating Nazi "atrocities" during its invasion of his country.
"Darkness has returned to Ukraine and it has become black and white again," he said in his video address.
Footage in the video showed the Ukrainian leader against a backdrop of destroyed residential buildings.
"Evil has returned, in a different uniform, under different slogans, but for the same purpose," he added.
The video also featured archive footage of World War Two and black-and-white footage of Russia's invasion.
When Ukraine was invaded by Russia in late February, Moscow maintained its operation was in part to "de-Nazify" the country.
Russian President Vladimir Putin returned to the theme in his own address congratulating former Soviet nations on the 77th anniversary of Nazi Germany's defeat, saying that "as in 1945, victory will be ours".
Ukrainian officials fear Russia may step up its attacks ahead of Russia's Victory Day commemorations on Monday.
Mr Zelensky appealed to European nations, including the UK, France and the Netherlands, by likening Nazi bombings of their towns and cities to Russian strikes on urban areas in Ukraine.
Later on Sunday, Ukraine's president is set to hold talks with G7 leaders - including US President Joe Biden and the UK's Boris Johnson - via video conference.
In another development, more than 60 people are now feared dead after a Russian bomb hit a school in eastern Ukraine on Saturday, local authorities said.
The governor of Ukraine's Luhansk region, Serhiy Haidai, said around 90 local residents had been sheltering in the school in the village of Bilohorivka, near the frontline in the Donbas region.