A 41-year-old U.S. Army soldier was arrested on suspicion of spying for Russia, British authorities announced Tuesday.

The unnamed soldier was arrested by U.K. counterterrorism police “working closely” with U.S. authorities, including the FBI and the military, the Metropolitan Police said in a statement. The man is in custody at a London police station.

“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,” FBI Director Kash Patel said in a statement issued by the British counter-terror police.

The man was arrested under sections of the U.K.’s National Security Act that cover espionage. The arrest occurred near Gloucester, a city about 100 miles west of London that is close to the home of GCHQ, Britain’s intelligence, security and cybersecurity agency.

“As part of the investigation officers are carrying out searches at two locations in Gloucestershire,” according to police. “The country to which the allegations relate is Russia.”

Brig. Gen. Sean Stinchon, the head U.S. Army Counterintelligence Command, said in a statement that the “senior soldier” who was arrested was “entrusted with sensitive information.”

Earlier this year, Britain’s spy chief warned that Russia is engaged in “daily hybrid activity” against the U.S. and its Western allies.

GCHQ Director Anne Keast-Butler accused Moscow of “relentlessly targeting critical infrastructure, democratic processes, supply chains and public trust” and that it attacks “from the seabed to cyberspace.”

The Kremlin did not immediately respond to a request for comment.