Washington's UN envoy accused Russia on Thursday of spinning "outright lies" on Ukraine designed to hide its direct involvement in the conflict in the east.

"The focus on Ukraine in the Security Council is important, because it gives me the chance -- on behalf of the United States -- to lay out the mounting evidence of Russia’s aggression, its obfuscation, and its outright lies," Samantha Power said in an address to a crowd of several hundred people in Kiev.