The suspects arrested over a potential terror plot near an RAF base used by the US are all British nationals aged in their 20s and from London, police have said.
The men were arrested in Whelford, Gloucestershire in the early hours of Sunday, initially on suspicion of explosives offences and later terrorism.
A villager in Whelford dialled 999 after she saw three vans and a group of masked men near the base, and dozens of homes had to be evacuated as bomb disposal teams were called in.
Counter Terrorism Police are understood to be investigating if any potential plot could be linked to Iran, which has used proxies to carry out crimes on British soil in the past.
On Monday, Counter-Terrorism Policing (CTP) said that multiple new lines of inquiry have emerged after investigators were working at the scene overnight.
CTP Senior National Coordinator, Deputy Assistant Commissioner Vicki Evans said: “This is a hugely complex and large-scale operation, involving local and national policing, the MoD, and local agencies, who are working together to progress the investigation and support for the community.
“I know this has been incredibly disruptive for local people, but I’d like to reassure them that our activity is in the interest of national security, but most importantly in the interest of their own safety.
“I’d also like to thank the emergency services for their response, including the armed officers who first attended the scene, not knowing what they may face.
“I am very aware of the levels of speculation about the motivation behind this incident, and the geopolitical questions that are being raised. However, I ask that at this time, Counter Terrorism Policing are given the space to work carefully and clearly.”
Iran’s embassy in London, though, put out a statement denying any involvement.
“The Embassy of the Islamic Republic of Iran in London categorically rejects and strongly condemns the recent unfounded and malicious speculations published by some British individuals and media outlets attempting to link Iran to arrest of five suspects in the vicinity of RAF Fairford base,” it said.
“The circulation of such fabricated speculations, particularly in the aftermath of the criminal acts of aggression committed by the United States and the Israeli regime against the Iranian people, will serve no purpose other than to fuel Iranophobia propaganda in the UK.
“The Islamic Republic of Iran reserves the right to take appropriate legal measures, as necessary, to safeguard the rights and interests of the country and its people in response to misleading and damaging media narratives.”
The five suspects are being held under the Police and Criminal Evidence Act, and officers have been granted an initial extension until later today to hold them in custody.
They are a 24-year-old from Camden, north London; three men aged 23, 24 and 25 from Westminster, and one aged 24 from Willesden, north-west London.
A police cordon remains in place in Whelford and will be reviewed later today, CTP said.
Gloucestershire Constabulary said it received reports of the suspicious vehicles travelling to the base at about 12.45am on Sunday.
Officers arrested the men under the Explosives Act, and they were later further arrested under suspicion of preparation of a terrorist act.
Suspects detained under the Terrorism Act 2000 can be held for up to 14 days without charge, compared to the 24-hour limit for standard arrests without an extension application.
Aerial footage showed a bomb disposal robot spending hours inspecting three white vans, two of which had open rear doors. Large black barrels appeared to be scattered around.
A 400-metre cordon was erected, and 85 evacuated households were unable to return home overnight. Cotswold District Council was seeking accommodation for some.
The army’s ordnance disposal unit was still examining the vehicles in the cordon by the evening, Temporary Chief Constable Maggie Blyth, from Bedfordshire Constabulary, told a press conference.
Agencies “believe the matter to be contained”, she later added.
Prime Minister Andy Burnham said the incident was “deeply concerning” and the government would “always take every step necessary” to protect people.
Investigators will now be working to analyse any devices seized from those arrested to establish details of any plot and any potential motivation.
The arrests come amid heightened concerns around the threat from hostile states to the UK, with Russia and Iran among those that have used proxies to commit crimes on their behalf on British soil.
In March, officials said the number of national security cases involving activity by hostile states, including Iran, increased by 50 per cent in the six months to December 2025.
That same month, after then-Prime Minister Sir Keir Starmer granted permission for “defensive” US action against Iranian missile sites from UK bases, four American bombers landed at RAF Fairford and the US started using British bases for “specific defensive operations”.
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