Three Bulgarian nationals suspected of spying on behalf of Russia have been arrested and charged by counter-terror detectives following a major national security investigation.

The BBC has revealed the defendants were held in February under the Official Secrets Act by Metropolitan Police officers and have been remanded in custody since.

The individuals, who are accused of working for the Russian security services, have been named as Orlin Roussev, 45, of Great Yarmouth, Norfolk, Bizer Dzhambazov, 41, of Harrow, north-west London and Katrin Ivanova, 31, of the same address

They have been charged with possessing identity documents with “improper intention”, which include passports, identity cards and other documents for the UK, Bulgaria, France, Italy, Spain, Croatia, Slovenia, Greece, and the Czech Republic, the BBC reported.

The trio have apparently lived in the UK for years and worked in a variety of jobs, according to a BBC investigation.

It found Mr Roussev has a history of business interests in Russia and moved to the UK in 2009.

He is said to have worked for three years in a technical role for a financial services company and a LinkedIn profile states he owned a business involved in the interception of communications or electronic signals.

The 45-year-old has also claimed to have worked as an adviser to the Bulgarian Ministry of Energy, it is reported.

While Mr Dzhambazov was described as a driver for hospitals by former neighbours in Harrow and Ms Ivanova has described herself as a laboratory assistant for a private health business on a LinkedIn profile.

The couple reportedly moved to the UK around a decade ago and ran a community organisation for Bulgarian nationals to help familiarise them with the “culture and norms of British society”.

The BBC, citing online Bulgarian state documents, reported the couple also worked for electoral commissions in London to facilitate voting in Bulgarian elections by nationals living abroad.

The defendants are due to stand trial at the Old Bailey in January and have yet to enter pleas to the charges.

News of the arrests emerged after the head of counter-terrorism at Metropolitan Police warned officers were increasingly dealing with threats from hostile states such as Russia, China and Iran in a shift in focus away from Islamist extremism.

Speaking in February, Matt Jukes said there had been a move by foreign states to attempt to corrupt or intimidate people as well as involvement in the murder and kidnap plots in Britain.

Previous high-profile Russian intelligence operations in the UK include the poisoning of defector Sergei Skripal and his daughter Yulia with the deadly nerve agent Novichok in 2018.

The Skripals were targeted in Salisbury, Wiltshire, and were treated at the hospital along with responding detective Nick Bailey but survived the attack.

However, Dawn Sturgess, who was unconnected to the Skripals, died after being exposed to Novichok.

Last month, Sir Richard Moore, the MI6 chief, issued an unprecedented call to Russians disaffected by Vladimir Putin’s “sheer callous incompetence” to spy for the UK.

Sir Richard Moore used a landmark speech to launch a recruitment campaign for defectors to “bring the bloodshed to an end” in Ukraine. He told them: “Our door is always open”, adding: “Come and talk to us.”