Britain is sending anti-drone equipment and Royal Air Force specialists to Belgium after a series of drone sightings near Belgian airports and military bases.

The deployments follow temporary closures at Brussels Airport and Liège cargo airport, as well as reports of drones near a base storing U.S. nuclear weapons.

U.K. military chief Air Chief Marshal Richard Knighton said the source of the drones remains unknown, but Britain is assisting Belgium at its request.

Defense Secretary John Healey emphasized that the move reflects NATO allies’ commitment to defending shared infrastructure and airspace, CBS News has reported.

The incidents are part of a wider pattern of unexplained drone activity across Europe, which some allies view as potential Russian hybrid warfare.