Russia said Saturday that it had expelled two U.S. diplomats Moscow claimed were working undercover for the CIA in retaliation for Washington’s explusion of two Russians last month.

The State Department announced Friday that it had expelled the two Russians on June 17, in response to an attack on an American diplomat outside the U.S. embassy in Moscow 11 days earlier.

State Department spokesman John Kirby said the attack was “unprovoked and it endangered the safety of our employee.”

The Russian Foreign Ministry claimed the American, who was one of the two expelled, was a CIA agent who refused to provide his identification documents and hit the guard in the face. Moscow says the policeman was fulfilling his duties defending the embassy.