British police have declared a major incident and evacuated homes near RAF Fairford, an air base in Gloucestershire, southwest England, used by US forces.

Several men were arrested early on Sunday morning on suspicion of offences under the Explosives Act, Gloucestershire Police said.

The army's specialist explosive ordnance disposal team is currently examining a number of vehicles, police said.

Residents from properties in Whelford, a town near RAF Fairford, were evacuated to a nearby leisure centre.

"We are working closely with our partners and are enacting the well-rehearsed plans we have in place," police said.

RAF Fairford has been used by US forces for operations against Iran.

A spokesperson for the US Air Force said personnel at the base remain vigilant.

"For operational security reasons we will not discuss specific force protection measures," the spokesperson said.

"The 501st Combat Support Wing and our fellow UK-based Wings remain vigilant and will take appropriate actions to ensure the safety and security of our US service members, civilians, contractors, and their families."

"We constantly assess a variety of factors that determine what measures we institute or modify to protect our installations, our people and their families," the spokesperson added.