Russia and the United States were locked in a fresh diplomatic slugging match Friday as Moscow accused Washington of threatening its citizens' security a day after it ordered the closure of Moscow's San Francisco consulate and two other facilities.
Russian foreign ministry spokeswoman Maria Zakharova said the FBI planned to search the San Francisco consulate on Saturday and accused the US authorities of threatening the "security" of Russian citizens and violating diplomats' immunity.
The spat between the two nuclear-armed powers is another blow to US President Donald Trump's pledge to try to improve relations with Russia's Vladimir Putin.
Washington ordered Russia on Thursday to shutter its San Francisco consulate along with two diplomatic annexes in Washington and New York by Saturday "in the spirit of parity."
Zakharova said in a statement that the FBI intended to carry out a search of the San Francisco consulate on Saturday "including of the apartments of employees who live in the building and have immunity," forcing them and their families to leave for up to 12 hours.
"We are talking about invasion into a consulate and the accommodations of diplomatic staff," Zakharova said. "The demands of the US authorities create a direct threat to the security of Russian citizens."
"We express a resolute protest over Washington's actions that ignore international law," Zakharova said, adding that: "We reserve the right to take retaliatory measures."
Her angry statement came after presidential aide Yury Ushakov was quoted by TASS news agency as describing the latest US measures as "a kind of illegal takeover."
"We will think how to respond," he added.
The US ordered the closures in a retaliatory move after the Kremlin demanded Washington slash staff numbers at its Russian diplomatic missions to 455 personnel with a deadline that ran out on Friday.
"The United States has fully implemented the decision by the government of the Russian Federation to reduce the size of our mission in Russia," State Department spokeswoman Heather Nauert confirmed in a statement.
Washington said it hoped the two sides "can avoid further retaliatory actions" and improve ties but warned it was "prepared to take further action as necessary and as warranted."
'Takes two to tango'
But top diplomat Sergei Lavrov avoided blaming the Trump administration for the latest tensions and laid the guilt squarely at the door of his predecessor Barack Obama.
"We are open even now for constructive cooperation where it corresponds to Russian interests," Lavrov said Friday.
"But it takes two to tango and so far our partner is, again and again, doing an individual break dance."
Lavrov is to meet his US counterpart Rex Tillerson in September in New York.
The fresh diplomatic spat is the latest twist in tortured ties between the US and Russia, which have slumped to their lowest point since the Cold War following the Kremlin's seizure of Crimea from Ukraine in 2014.
The West slapped punishing sanctions on Russia over its meddling in its ex-Soviet neighbour, sparking a revenge embargo from Moscow against agricultural products.
'Hysterical impulses not useful'
Last year tensions ramped up again after the US intelligence community accused Putin of masterminding a hacking and influence campaign to tip the presidential vote in favour of Trump.
In the waning days of his tenure, Obama hit out at Russia over the allegations by turfing out 35 diplomats and closing two of Moscow's diplomatic compounds.
Moscow initially held off from retaliating but when Congress passed new sanctions tying up Trump's hands, the Kremlin decided to belatedly strike back and ordered the US staff cut.
Any impression that he is cosying up to Russia has become politically toxic for Trump amid a string of probes into potential collusion between his team and the Kremlin.
Thursday's announcement by the State Department came as Russia's new ambassador to Washington, Anatoly Antonov, arrived in the US capital to take up his post, Russian news agencies reported.
"Right now we need to calmly examine (this situation). We should act calmly and professionally," Antonov told RIA-Novosti.
"As Lenin said, hysterical impulses are of no use to us."
Antonov's predecessor Sergei Kislyak is one of the figures at the centre of the scandal over alleged Russian meddling in the November election in a bid to help Trump beat Democrat Hillary Clinton.