UK counterterrorism police arrested a 27-year-old dual British-Iranian national in Westminster, London, on Thursday on suspicion of preparing terrorist acts, bringing the number arrested in the RAF Fairford investigation to six. A separate 26-year-old British man was questioned under caution. Police are investigating possible foreign state involvement in the incident near the base, which US bombers have used for operations against Iran.

Five British men aged 23 to 25 who live in London were arrested near Fairford on Sunday after reports of three suspicious vehicles heading toward the base. They were released on police bail on Monday and remain under investigation, with strict restrictions on their movements and contacts. Police recovered petrol from the vehicles but found no improvised explosive devices.

Prime Minister Andy Burnham said Wednesday there were “strong indications that Iran played a part,” while stressing that the investigation remained ongoing. The Wall Street Journal reported, citing an official familiar with the intelligence, that a branch of Iran’s Revolutionary Guards recruited British nationals for a plot to attack aircraft and kill personnel, involving multiple steps and a diversion nearby. Iran denies involvement and summoned British Ambassador Hugo Shorter on Thursday to protest allegations it called “baseless.” Foreign Minister Abbas Araghchi rejected Burnham’s assertion, saying: “You're barking up the wrong tree.”