The unlawful continuing detention of Ukrainian citizen Nadia Savchenko in Russian prison is a violation of the Minsk agreements on the settlement of the crisis in eastern Ukraine, U.S. Vice President Joe Biden said on Tuesday.

"Her unlawful continuing detention is a clear violation of Russia's commitment under the Minsk agreements, and she should be freed at once," Biden said in a statement posted on the White House.

"Nadia has been unjustly imprisoned in Russia since 2014—detained and facing trial on trumped up charges. Nadia was proudly serving her country as a member of the Ukrainian armed forces, fighting in the eastern part of the country when she was abducted by separatists and taken across the border against her will," the vice president said.

He called on Russia to drop all charges against Savchenko and release her at once.

"Nadia deserves to go home to her family and friends and join her fellow Rada members to begin shaping a new Ukraine," Biden said.