British police arrested a senior US Army officer on Tuesday on suspicion of spying for Russia, NATO confirmed on Wednesday.

The 41-year-old man was detained near Gloucester in southwest England under Sections 1 and 3 of the National Security Act 2023. The charges cover disclosing protected information and assisting a foreign intelligence service. Police specified that the country concerned is Russia. The arrest was conducted in close collaboration with US authorities following a joint investigation with the FBI and US military intelligence. He was taken to London and remains in custody, where he can be held for up to 14 days without charge. Searches continued at two locations in Gloucestershire on Wednesday.

The suspect was assigned to NATO's Allied Rapid Reaction Corps, based at Imjin Barracks in Innsworth, Gloucestershire. A senior NATO military official confirmed the arrested service member belonged to the corps. The ARRC coordinates the alliance's warfighting effort in the event of an invasion and can deploy across Europe to reinforce defenses. Military chiefs said the officer had been "entrusted with sensitive information" in his role.

Kremlin spokesman Dmitry Peskov denied any Russian involvement on Wednesday. "This arrest does not concern us in any way, and we do not know what it is connected to," he said. FBI Director Kash Patel called it a "significant arrest" and said the bureau has "zero tolerance" for anyone who betrays their oath. Brigadier General Sean Stinchon, head of US Army counterintelligence, described the suspect as a "senior-ranking soldier entrusted with sensitive information." He called the alleged acts a "sobering reminder that insider threats are real and persistent." Vicki Evans, the UK's counterterrorism coordinator, said the allegations are serious and the investigation is ongoing.

The ARRC headquarters is NATO's largest base in the UK. It houses more than 400 permanent personnel from over 20 allied countries and sits near the headquarters of GCHQ, Britain's cyber-intelligence agency. In his annual threat update, MI5 chief Sir Ken McCallum warned that Russia remains "aggressor number one," with the West facing a "long-haul contest."