The BBC understands the man was based at Imjin Barracks in Gloucestershire

A soldier in the US Army has been arrested on suspicion of spying for Russia, British counter-terror police have said.

The 41-year-old senior serviceman was arrested near Gloucester on Tuesday.

Counter Terrorism Policing London said the man had been arrested under section one and section three of the National Security Act 2023.

Section one of the Act relates to obtaining or disclosing protected information, while section three relates to assisting a foreign intelligence service.

As part of the investigation, officers are carrying out searches at two locations in Gloucestershire.

The BBC understands the soldier was based at Imjin Barracks in Innsworth, Gloucestershire. The barracks serve as the headquarters of Nato's Allied Rapid Reaction Corps (ARRC), a strategic operational base for the alliance.

Counter Terrorism Policing said it was not linked to any other ongoing investigations.

FBI director Kash Patel said in a statement: "This important arrest involves allegations of espionage, which is of the utmost concern to the United States and our allies."

He added: "While this investigation is continuing, I want to send a clear message – this FBI has no tolerance for anyone who breaks their oath to the United States and whose actions endanger our national security and that of our partners."

Deputy Assistant Commissioner Vicki Evans, from Counter Terrorism Policing London, described the arrest as "significant".

"The allegations are serious and our investigation is very much ongoing," she said.

The unnamed soldier is currently in custody at a London police station.

He has been detained under the National Security Act 2023, allowing police to hold him without charge for up to 14 days.

Brig Gen Sean Stinchon, commanding general of US Army Counterintelligence Command, said: "The alleged conduct of a senior soldier, entrusted with sensitive information, is a sobering reminder that insider threats are real and persistent.

"I encourage anyone who thinks they've witnessed something suspicious to report it to their local counterintelligence office."

Additional reporting by Daniel Sandford, UK correspondent.