LONDON: Ukraine is examining the alleged culpability of 500 Russian leaders for thousands of war crimes, including President Vladimir Putin, a top official said on Sunday.

Speaking on Britain’s Sky News, Ukrainian prosecutor general Iryna Venediktova also thanked Prime Minister Boris Johnson for his surprise visit to Kyiv on Saturday.

Johnson promised more UK military aid in face-to-face talks with President Volodymyr Zelensky, before the pair took a heavily guarded stroll through central Kyiv.

“I think that the Ukrainians have shown the courage of a lion, and you, Volodymyr, have given the roar of that lion,” Johnson said in televised remarks, standing alongside the president.

Venediktova said Johnson’s trip had offered “really great support for us”, as she detailed alleged atrocities by Russian invaders, including at a railway station packed with fleeing civilians.

Dozens of civilian Ukrainians found in grave near Kyiv

“Of course what we see on the ground in all the regions of Ukraine, it is war crimes, crimes against humanity,” the prosecutor added, speaking in English.

She said there was “full evidence” linking Russian forces to the missile attack on the station at Kramatorsk, in eastern Ukraine, where officials said 52 people were killed.

“That’s why it will be one of the cases in our big profile,” Venediktova said.

“You know that now we started 5,600 cases in Ukraine on the above war crimes”, involving “500 suspects” from Russia’s government and military, she said.

“Vladimir Putin is the main war criminal of 21st century,” the official said, adding that as president, he may enjoy immunity from prosecution under international law but that would not last forever.

A week ago, Zelensky said that he had created a “special mechanism” to investigate Russian “war crimes” in Ukraine, vowing to find and punish “everyone” responsible.

The mechanism would include national and international experts, investigators, prosecutors and judges, he said.

Britain has been providing technical expertise as the International Criminal Court in The Hague pursues its own investigation into the Ukraine invasion.

In Kyiv, Johnson said the discovery of civilian bodies in Ukrainian towns such as Bucha and Irpin had “permanently polluted” Putin’s reputation and amounted to war crimes.