MOSCOW (Reuters) – Russia’s foreign ministry has summoned a U.S. diplomat in Moscow to hand him a note of protest over plans to conduct searches in Russia’s trade mission complex in Washington, which should soon be closed, the ministry said in a statement on Saturday.

It said it has summoned Anthony F. Godfrey, a deputy chief of mission at the U.S. Embassy in Moscow.

The ministry called the planned “illegal inspection” of Russian diplomatic housing an “unprecedented aggressive action”, which could be used by the U.S. special services for “anti-Russian provocations” by the way of “planting compromised items”.

The closure by Sept. 2 of the consulate and buildings in Washington and New York that house Russian trade missions is the latest in tit-for-tat actions by the two countries that have helped push relations to a new post-Cold War low.

The Kremlin has said the moves to close the Russian facilities pushed bilateral ties further into a dead end.

On Friday, the Russian foreign ministry also said the U.S. special services were prepared for searches in its consulate in San Francisco.

Some media reported that a smoke was billowing from a chimney of the building. Maria Zakharova, the spokeswoman for the ministry, said it was part of a “mothballing”.

“In relation to this, the windows could be closed, the light could be turned off, the water could be drained out, the heating appliances could be turned off, the garbage could be thrown away, essential services could be turned off and many other things,” she wrote on social media.

Moscow last month ordered the United States to cut its diplomatic and technical staff in Russia by more than half, to 455 people to match the number of Russian diplomats in the United States, after Congress overwhelmingly approved new sanctions against Russia.