UNITED NATIONS — The United States says it is expelling 12 Russian diplomats at the United Nations for engaging in activities not in accordance with their responsibilities and obligations as diplomats.

U.S. deputy ambassador Richard Mills confirmed the expulsions after Russia’s U.N. Ambassador Vassily Nebenzia told the U.N. Security Council on Monday afternoon that he had just been informed of “yet another hostile step undertaken by the host country" against the Russian Mission.

Nebenzia called the U.S. expulsions a “gross violation” of the U.N. agreement with the United States as the host of the United Nations and of the Vienna Convention governing diplomatic relations.