BREAKING: U.K. Prime Minister Andy Burnham says there are "strong indications" Iran played a part in the security incident outside RAF Fairford, a British air base used by U.S. forces.

Five British men in their 20s were arrested after three suspicious vehicles were found near the base. Police recovered gasoline but found no explosives, and all five suspects have since been released on strict bail as the counterterrorism investigation continues.

Burnham stresses the investigation remains "complex and serious" and says British authorities are working closely with the United States. Iran has strongly denied any involvement.