A UK-Iranian dual national arrested on suspicion of preparation of terrorist acts in connection with an incident at RAF Fairford has been released on bail.

The 25-year-old man was arrested in the London borough of Westminster on Thursday. Searches of two properties in the same area have since concluded.

A major incident was declared and dozens of homes were evacuated after police were alerted to three suspicious vehicles near the airbase in Gloucestershire last weekend.

Five other men in their twenties were arrested in connection with the same incident and were subsequently released on police bail. All five were UK nationals from London.

The five men, aged between 23 and 25, were detained in the early hours of the morning after vehicles were reported to be travelling towards the base, which is operated by the US Air Force. According to reports, one of the men had dialled 999 himself, approximately an hour before a local farmer alerted police to a large group of masked men near the vehicles.

They were arrested on suspicion of explosives offences and later on suspicion of preparing a terrorist act, before being released on bail on Monday in what police described as an "investigative decision" that was "grounded in experience and strategy".

The investigation into the circumstances surrounding the events is continuing, police said.

Prime Minister Andy Burnham chaired a Cobra meeting on Monday afternoon in response to the incident. He later said there were "strong indications" that Iran had played a part, but did not provide further details.

Tehran has strongly denied any involvement. The Iranian embassy in London said on Monday that it "categorically rejects and strongly condemns" what it called "unfounded and malicious speculations" linking Iran to the incident.

RAF Fairford has served as a forward operating location for the US Air Force for decades. In recent months, US bombers have taken off from the base for operations in the Middle East, after the UK approved a US request to use it for defensive strikes on Iran. In July, Iran stated that "any base used for aggression against Iranian territory constitutes a legitimate target for our forces".

US Secretary of State Marco Rubio said late on Monday that it was clear a foreign actor had been involved in the weekend's events. Speaking on a television programme without providing evidence or further details, he said: "What happened, what almost happened, what could have happened in the UK over the weekend is a very serious situation. It's one that clearly involves the hands of a foreign actor."

Speaking earlier at the Oval Office, US President Donald Trump said he would not have released the five men on bail and that he was "surprised" by the decision.

"We know everything about them, we would not have released them," Trump said, adding that the UK had worked with the United States "very closely" on the matter.