Russia declared nine members of the Polish embassy in Moscow "persona non grata" on January 22 and demanded they must leave Russia before January 28.

Meanwhile, the Polish ambassador to Russia received a corresponding note at the Russian Foreign Ministry, which accounts the decision to the activities of the diplomats incompatible with their status and provisions of the Vienna Convention.

The move was a reply to the Thursday demarche of the Polish government that expelled nine Russian diplomats from the embassy in Warsaw.

Earlier Friday Russian Foreign Minister Igor Ivanov said Russiawill adopt the "most ruthless adequate measures" in response to Poland's expulsion of Russian diplomats. He described Warsaw's actions as "an unprovoked provocation."

"It is hard to say now whether the decision was adopted immediately in Warsaw or by anyone's prompting. But in any case the step injects an additional complexity in our relations with Poland," Ivanov said.