Russian authorities expelled several European diplomats in recent days amid growing tensions between Moscow and the West over Russia's role in Ukraine's instability.
Several Polish diplomats were told to leave in response to the recent expulsion of Russian diplomats from Poland, Russian authorities said Monday.
"To our deep regret the Polish authorities did really undertake such an unfriendly step, unjustified by anything," Russian Foreign Ministry spokesman Alexander Lukashevich was quoted as saying in a statement posted on the agency's official website.
"In this connection," the statement added, "the Russian side took adequate response measures and a number of Polish diplomats have already left the territory of our country for the activities incompatible with their status."
The statement did not specify how many diplomats were expelled, but a Federal Security Service officer said four Polish diplomats were sent home late last week.
"It was a tit-for-tat measure, nothing personal," said the officer, who requested anonymity while discussing a sensitive issue. "This is standard practice as Russia demonstrated that it wouldn't leave any such step on the part of our Western partners without retaliation."
Polish authorities arrested a Polish officer last month on suspicion of spying for a foreign country, Russia's RIA Novosti news service reported. Later in October, the Polish Agency of Internal Security requested that a number of Russian diplomats be expelled, the report said.
A German diplomat also left Russia last week at Moscow's request following the expulsion of a Russian diplomat from a mission in Germany, RIA Novosti reported.
The expulsion could only further aggravate the tense relations between Russian and the West over Ukraine, an analyst said.
"The scandal over the expulsion of Polish diplomats and especially the kicking out of a German diplomat signify a deepening rift between Russia and the West, given the deepening political crisis over Western accusations of Russian involvement in Ukraine's violence," said Andrei Kotunov, president of New Eurasia Foundation, a Moscow-based think tank, in an interview to The Times.