The Russian Foreign Ministry on Wednesday informed the U.S. Embassy in Moscow that 10 of its staffers must leave the country by the end of May 21 in tit-for-tat retaliation.
The ministry said in a statement that it summoned deputy chief of the U.S. mission Bartle Gorman and gave him a note declaring these people "persona non grata."
The ministry called the decision a mirror-like response to the "unreasonable" expulsion of staffers at the Russian Embassy in Washington and the Russian Consulate General in New York.
The ministry vowed to take further steps in the near future, as announced on April 16, in response to a recent series of "illegal" U.S. sanctions against Russia.
The ministry on Friday announced a package of countermeasures, including the expulsion of 10 U.S. diplomats and an entry ban on eight incumbent and former American high-ranking officials.