A U.N. commission set up to investigate possible war crimes in Ukraine during the Russian invasion said on Wednesday it had not yet not managed to establish contact with Russia.

Erik Mose, who heads the independent panel, told a news conference during a visit to Kyiv that efforts to start dialogue with Russia's mission in Geneva had "not been successful" but that the commission would keep trying to make contact.

The commission was created by the U.N.'s Geneva-based Human Rights Council (UNHRC) to investigate alleged abuses of human rights and international humanitarian law during the invasion launched on Feb. 24.

Mose said it was too early to discuss details of evidence collected in Kyiv, in the eastern cities of Kharkiv and Sumy, and in the towns of Irpin and Bucha where Ukraine says Russia committed large-scale atrocities. Russia denies the allegations.

"In Bucha and Irpin, the commission received information about arbitrary killing of civilians, destruction and looting of property, as well as attacks on civilian infrastructure, including schools," Mose said.

The International Criminal Court has opened a separate inquiry into alleged war crimes and crimes against humanity in Ukraine. The office of Ukraine's prosecutor general said on Wednesday that ICC Prosecutor Karim Khan had visited Kharkiv to view evidence of alleged war crimes, but gave few details.

Russia denies targeting civilians in its "special military operation" to disarm and "denazify" Ukraine. Kyiv and its allies say the invasion is an unprovoked war of aggression.

In the first war crimes trial arising from Russia's invasion, a Ukrainian court last month sentenced a Russian soldier to life in prison for killing an unarmed civilian in Ukraine.

A court in the self-proclaimed Donetsk People's Republic last week sentenced two Britons and a Moroccan to death for "mercenary activities" seeking to overthrow the republic.