Moscow (CNN) -- Russia said Wednesday that it blamed "unfriendly" actions by Britain for a recent diplomatic spat that led both nations to expel each others' diplomats.
"The British side has recently took an unfriendly step, groundlessly declaring persona non grata a diplomat at the Russian Embassy in London. We were compelled to take a similar step in response," a statement on the Russian Foreign Ministry said.
"It is regretful that the actions of the British side were undertaken at a moment when our relations with Britain have just started to improve. The initiators of this incident bear full responsibility for its consequences."
The statement comes after the United Kingdom expelled a Russian diplomat on suspicion of spying, and Russia kicked out a British embassy staffer in Moscow in retaliation.
Britain asked the Russian to leave on December 10 "in response to clear evidence of activities by the Russian intelligence services against U.K. interests," British Foreign Secretary William Hague said Tuesday.
Russia told the British diplomat to leave Moscow on December 16, Hague said.
Hague said there was not "any basis" for the expulsion.
CNN's Maxim Tkachenko contributed to this report.