0650 GMT May 20, 2019
Moscow also said it would halt the activities of the British Council in Russia in a tough series of retaliatory measures announced after it summoned British ambassador Laurie Bristow, AFP reported.
British Prime Minister Theresa May responded defiantly to the tit-for-tat move, which followed Britain's expulsion of 23 Russian diplomats and the suspension of high-level contacts earlier this week.
She told a forum of her Conservative Party that Britain had "anticipated a response of this kind" and that it "will consider our next steps in the coming days, alongside our allies and partners".
She also repeated accusations made by Britain to the United Nations that the nerve agent attack on Sergei Skripal and his daughter Yulia in the English city of Salisbury on March 4 was a "flagrant breach of international law and the Chemical Weapons Convention."
The crisis erupted after the Skripals were exposed to a nerve agent that British officials say was developed in Russia, leaving them in critical condition.
London and its allies have blamed Moscow for the attack and on Friday, Britain directly implicated Russian President Vladimir Putin himself, unleashing the Kremlin's fury.
"Twenty three diplomatic staff at the British embassy in Moscow are declared persona non grata and to be expelled within a week," a Foreign Ministry statement said.
It said this was a response to Britain's "provocative actions" and "baseless accusations over the Salisbury incident.
Russia also said it was closing Britain's consulate in the city of Saint Petersburg, citing a "disparity" in the number of diplomatic missions held by the two countries.
And it said it had halted the activities of the British Council, Britain's international organization for cultural relations and educational opportunities.
The group said it was "profoundly disappointed" at the move.
The Russian ministry also warned Britain that it "retains the right to take other answering measures" in response to any "further unfriendly actions."
Skripal had taken his daughter, who was on a visit from Moscow, out for lunch in Salisbury before they both collapsed on a bench.
Russia insists it had no motive to target Skripal with what Britain says was a highly-potent nerve agent called Novichok, in the first such attack in Europe since World War II.
On Friday, Kremlin spokesman Dmitry Peskov said statements by British Foreign Secretary Boris Johnson tying Putin to the attack were "shocking and unforgivable".