The diplomats' activities threatened Russia's security and were aimed at ensuring Moscow's defeat in its war against Ukraine, according to domestic media.
ADVERTISEMENTSix British diplomats in Russia have been accused of spying and have had their accreditation revoked, the Kremlin's security agency FSB said on Friday.
Russian state TV quoted an FSB official as saying that they would be expelled.
The FSB claimed that it received documents indicating that they were sent to Russia by a division of the UK Foreign Office “whose main task is to inflict a strategic defeat on our country” and that they were involved in “intelligence-gathering and subversive activities".
The move comes two days after the US and UK pledged nearly €1.35 billion in additional aid to Kyiv and as Ukrainian officials renewed their pleas to use Western-provided missiles against targets deeper inside Russia.
The FSB warned that "if similar actions are detected among employees of the British diplomatic mission, the FSB will demand early termination of their missions in the Russian Federation."
The move came as British Prime Minister Keir Starmer arrived in Washington for talks with US President Joe Biden on allowing Ukraine to fire missiles supplied by the West into Russia.