Moscow has threatened retaliation following the U.S. seizure of a Russian consulate building in San Francisco, a month after its diplomats were ousted from the property.

Local media reported that U.S. State Department officials searched the Russian general consulate in San Francisco on Monday.

The building and several other consular properties in the U.S. were vacated by Russian diplomatic staff in early September, on Washington’s orders. The move came after Moscow instructed the U.S. diplomatic mission in Russia to cut its staff by hundreds of people in a series of tit-for-tat measures between the two countries.

On Monday, almost a month after the move, Russia’s Foreign Ministry published a new statement, hinting at new measures.

“We strongly protest this latest hostile act of the United States and reserve the right to respond,” it said.

The ministry repeated previous allegations that U.S. law enforcement had broken down and conducted searches at the residence in “flagrant” violation of international law.

“Nobody has invited U.S. agents to be there. They are intruders,” the statement reads. “Their actions are outrageous and unprecedented in the history of bilateral relations.”

The ministry also published video updates of the “invasion into Russian diplomatic property” on its Facebook page.