Russia will expel 23 British diplomats in a tit-for-tat reaction to Theresa May's response to the nerve agent attack on Sergei and Yulia Skripal.
The country's Ministry of Foreign Affairs announced it had ordered the diplomats to leave within a week, moments after Britain's ambassador to Russia Laurie Bristow left the ministry in Moscow.
Other measures included closing the British Council and scrapping an agreement to reopen the British consulate in St Petersburg, while the country indicated it could take further action should there be what it called more "unfriendly" moves, the Associated Press reported.
Mr Bristow, speaking to reporters after being summoned, said the UK would "always do what is necessary to defend ourselves, our allies and our values against an attack of this sort".
It comes after NHS England said Detective Sergeant Nick Bailey, the police officer exposed to the Novichok agent in Salisbury, is no longer in a critical condition.
But Mr Skripal, 66, the Russian ex-spy who was the target of the attack, and his daughter Yulia, 33, remain critical but stable in hospital.
Russia has opened its own criminal investigation into the attempted murder of Yulia, a Russian citizen, and also Nikolai Glushkov, a Russian exile Scotland Yard said died from "compression to the neck" at his home in New Malden, south-west London.
British police are not linking his case with the Salisbury attack.
Foreign Secretary Boris Johnson said on Friday it was "overwhelmingly likely" that Vladimir Putin directed the use of the nerve agent on Britain's streets.
Speaking during a visit to the Battle of Britain Bunker museum in Uxbridge alongside the Polish foreign minister, Jacek Czaputowicz, Mr Johnson said: "Our quarrel is with Putin's Kremlin, and with his decision - and we think it overwhelmingly likely that it was his decision - to direct the use of a nerve agent on the streets of the UK, on the streets of Europe, for the first time since the Second World War."
Mr Johnson's move to publicly blame Mr Putin was understood to have been a deliberate decision rather than an off-the-cuff gaffe.
It is thought Mr Johnson may have seen information which enabled the Government to come to that conclusion.
Echoing Mr Johnson's remarks, Mr Czaputowicz said: "We are sure that it is the Russian state which is involved in this attempt. It is certain."
The Foreign Secretary's comments were rebuked by Mr Putin's spokesman Dmitry Peskov, who said: "Any reference or mentioning of our president is nothing else but shocking and unpardonable diplomatic misconduct."
And Russia's ambassador to London, Alexander Yakovenko, suggested the Government was using the incident to divert attention from Brexit.
Mr Yakovenko said that Britain had put its weight behind an "anti-Russian campaign" as it tried to establish a new place for itself within Western society after EU withdrawal.
Speaking to the Russian state-funded RT television network, the ambassador denounced Britain's decision to expel 23 diplomats as "unacceptable and unjustified".
Sunday is set to mark two weeks since the incident.