Amnesty International said on Wednesday it had documented evidence of war crimes by both sides in the conflict between Ukrainian forces and pro-Russian separatists in eastern Ukraine.
The human rights group's secretary general, Salil Shetty, told a news conference that some separatists and Ukraine's Aidar battalion had committed human rights abuses in the five-month-old conflict.
"Amnesty international has called the conflict in Ukraine an international conflict and Russia a party to that conflict," he said.
Russia had denied it is a party to the conflict and has dismissed accusations that it has sent soldiers and weapons to support the separatists.