Five people were arrested in the UK on suspicion of breaching the Official Secrets Act, police said on Tuesday, with reports they were detained for allegedly spying for Russia.

London's Metropolitan Police said four people -- two men aged 31 and 42, and two women aged 29 and 32 -- were detained in the British capital on February 8 this year.

The fifth -- a 45-year-old man -- was held at an address on the Norfolk coast in eastern England.

None of the five was charged under the Official Secrets Act, but three of them -- Orlin Roussev, 45, from Great Yarmouth in Norfolk; Biser Dzambazov, 42, from Harrow, northwest London; and Katrin Ivonova, 32, also of Harrow -- were charged with identity fraud.

Police confirmed to AFP the three charged were Bulgarian nationals.

"All five individuals were later released on police bail and are due to return in September 2023,".

The three charged appeared in court in central London on February 13 each charged with "possession of false identity documents with improper intention", a police statement read.

The trio made another court appearance on July 31, and were remanded in custody until a date to be fixed, it added.

The BBC said the initial arrests were made because of suspicion of links to the Russian security services.

But there was no immediate confirmation of the report.

The Met is Britain's biggest police force and has national responsibility for matters involving espionage.