MOSCOW (AP) — Russian authorities on Tuesday ordered a British diplomat to leave the country on allegations of spying that the U.K. dismissed as “baseless” as tensions soar over the conflict in Ukraine.

Russia's Federal Security Service, the top domestic security and counterintelligence agency, said in a statement carried by Russian news agencies that the diplomat had provided false personal data while seeking permission to enter the country.

The agency, known by its Russian acronym FSB, alleged that he has worked for British intelligence under diplomatic cover, replacing one of the six British diplomats who were expelled from Russia in August. The FSB alleged that the diplomat was involved in “intelligence and subversive activities that threatened the security of the Russian Federation.”

Russia's Foreign Ministry spokesperson Maria Zakharova said a decision was made to revoke the diplomat's accreditation and he has been ordered to leave the country within two weeks. She said the ministry has summoned the British ambassador to hand over the notice.

A spokesperson for the U.K. Foreign Office responded to the Russian statements: "This is not the first time that Russia has made malicious and baseless accusations against our staff. We will respond in due course.”

Russia announced the expulsion of the six British diplomats in September, weeks after it happened. Moscow accused them of spying, allegations rejected by the U.K. as “completely baseless.”

Russia and NATO allies have carried out multiple rounds of mutual expulsions of diplomats as relations have sunk to the lowest levels since the Cold War after the Kremlin sent troops into Ukraine in February 2022.