Russia has expelled a British diplomat from its Moscow embassy, accusing him of espionage, according to Russian state media reports.
The diplomat has been stripped of his accreditation and ordered to leave Russia within two weeks, the state news agency TASS reported.
Russia's FSB security service claimed the diplomat had carried out "intelligence and subversive work" that threatened the country's security.
The Russian Foreign Ministry has also summoned British Ambassador Nigel Casey to Moscow, spokeswoman Maria Zakharova said.
Nigel Casey has been summoned to MoscowReuters
British Ambassador to Russia Nigel Casey leaves the Russian Foreign Ministry in Moscow
Reuters
The UK Foreign Office had at the time said the expulsions were part of a campaign to deter Britain's support for Ukraine.
There has been no immediate comment from the British Foreign Office or the British Embassy in Moscow regarding today's expulsion.
Relations between Britain and Russia have plunged to post-Cold War lows since the start of the Ukraine war, with Britain joining successive waves of sanctions against Moscow.
Tensions escalated further last week after Ukraine used British-supplied Storm Shadow missiles to strike targets inside Russia for the first time.
Russian President Vladimir Putin responded by launching a new experimental ballistic missile at the Ukrainian city of Dnipro on November 21.
Putin cited both the Storm Shadow strikes and Ukraine's use of US-supplied ATACMS missiles as justification for the response.
Russian President Vladimir Putin speaking in the Kremlin
Reuters
Footage showed Ambassador Casey's car arriving at the Ministry of Foreign Affairs in Moscow following his summons.
The latest expulsion follows a series of diplomatic rows between the two nations this year.
In May, Britain expelled Russia's defence attaché in London, claiming he was an undeclared military intelligence officer.
Moscow retaliated by ordering the British defence attaché to leave Russia.