British police said on Tuesday they had charged two men and a woman with identity document offenses after the BBC reported the group was accused of spying for Russia.
The individuals are Bulgarian nationals, who were alleged to be working for Russian security services, the BBC said in its report, saying they had been held as part of a major national security investigation.
London's Metropolitan Police confirmed five people had been arrested by counter-terrorism officers in February under the Official Secrets Act and three had since been charged with possession of false identity documents with improper intention.
A police statement named them as Orlin Roussev, 45, Biser Dzambazov, 42, and Katrin Ivanova, 31. They appeared at London's Old Bailey Court in July and were remanded in custody until a future date.
The police declined to comment on whether they were suspected of being Russian spies.
Britain has been sharpening its focus on external security threats and last month it passed a new national security law, aiming to deter espionage and foreign interference with updated tools and criminal provisions.
The government labeled Russia "the most acute threat" to its security when the law was passed.
Police have charged three Russians, who they say are GRU military intelligence officers, with the 2018 attempt to murder former double agent Sergei Skripal with the military-grade nerve agent Novichok. Two were charged in 2018 and the third in 2021.
Last year, Britain's domestic spy chief said more than 400 suspected Russian spies had been expelled from Europe.
Britain has also been one of the strongest supporters of Ukraine since the Russian invasion last year and has imposed a range of sanctions on Russian officials and oligarchs.