Ukrainian authorities are gathering evidence for potential war crimes committed by Russian forces, Kyiv's Ambassador to Washington Oksana Markarova said Friday.

Markarova noted that the evidence was being collected for launching international prosecution against Moscow.

Earlier on Friday, the country's Foreign Minister Dmytro Kuleba said Russia attacked a kindergarten and an orphanage in Ukraine during their invasion.

"Together with the General Prosecutor's Office we are collecting this and other facts, which we will immediately send to The Hague. Responsibility is inevitable," Foreign Minister Kuleba said on Twitter.

At a news conference in Washington, Markarova also said Ukrainian President Volodymyr Zelenskyy held a "very productive" phone call with President Joe Biden on Friday.

Amnesty International: Russia's attacks mean civilian deaths

The Russian invasion of Ukraine has been marked by indiscriminate attacks on civilian areas and strikes on protected objects such as hospitals, human rights organization Amnesty International said.

Such indiscriminate attacks violate international humanitarian law and may constitute war crimes, Amnesty said, adding that its staff had documented three incidents thought to have killed at least six civilians and injured at least 12 more.

Amnesty also said the Russian military leadership was falsely claiming to use only precision weapons. "The Russian military has shown a blatant disregard for civilian lives by using ballistic missiles and other explosive weapons with wide-area effects in densely populated areas," said Agnès Callamard, Amnesty International’s Secretary-General.