Five men have been arrested and remain in custody following a counter‑terrorism investigation near RAF Fairford, Gloucestershire Police said.
The force reported receiving a telephone call at approximately 00:45 BST concerning “three suspicious vehicles” heading toward the airfield.
As a precaution, residents of the nearby village of Whelford were evacuated to a local leisure centre while enquiries continue.
BBC correspondent Duncan Kennedy is on site at the base, which the United States Air Force has utilized to launch strikes against Iran since March.