Iran categorically denied involvement on Monday in a suspected plot to attack a British airbase used by the United States to strike Iranian sites, just as British police announced they were releasing on bail five men arrested over explosives and terrorism offences.

In a statement on X, Iran’s embassy in London said it “categorically rejects and strongly condemns the recent unfounded and malicious speculations”.

It said claims in the British media linking Tehran to the incident would only fuel “Iranophobia propaganda” in the UK.

The five men, British nationals from London in their mid-20s, were arrested early on Sunday after police were alerted to three suspicious white vans heading towards RAF Fairford in Gloucestershire, which houses US bombers that fly missions against Iran.

Police said on Monday the men had been released on bail after extensive inte­rviews and inquiries. But Laurence Taylor, the assistant commissioner and head of Counter Terrorism Policing, said this did not mean the investigation was over.

Officers were considering the incident “from every possible angle”, he told reporters, “including that this may be activity committed by proxies, or individuals either knowingly or unknowingly, working on behalf of a foreign state”.

Counter Terrorism Policing Senior National Coordinator Vicki Evans said she was aware of speculation about the motive and geopolitical questions that were being raised, but asked that police be given “the space to work carefully and clearly”.

Meanwhile, British Prime Minister Andy Burnham called an emergency meeting of senior officials to ensure they had “the full picture”. He pulled out of several events at Labour’s annual conference on Sunday to monitor the situation.

Authorities have not confirmed the exact nature of the threat. A bomb disposal robot was seen operating around the vans, which were examined by forensic experts with military support. Armed police guarded the main entrance to the base while heavy machinery blocked other access points.

A farmer from the nearby village of Whelford, who alerted police after seeing “hooded and masked men” running into fields, said she believed her 999 call had foiled any plot. Speaking anonymously, she said she believed police had “dropped the ball” over the threat.

The defence secretary, Wes Streeting, told the BBC the farmer had only a “partial picture” of the investigation. He declined to speculate about motives during a live inquiry but said the UK faced a general threat from Iran.

“We know that Iran and their proxies wish to do us harm,” he said. “We know that they hate our democracy, and we know that we regularly have to thwart Iranian attempts to threaten either our interests or indeed our allies.”

After the Fairford arrests, the US Emb­assy issued a security alert saying US citizens should “exercise caution” and be “mind­ful of personal security”. Security was stepped up at other US airbases in Britain. Donald Trump, speaking during a visit to Chicago on Sunday, said the suspects had been looking to do “big damage to our fort” and had been under investigation by British and American authorities.

“You’ll be hearing about it very soon. We caught them,” the US president said, appearing to nod when asked about an Iranian connection.

In March, the UK government authorised the US to use bombers based at Fairford to strike Iranian missile sites that were attacking ships in the Strait of Hormuz.

After the arrests, police put a 400-metre cordon around the base and evacuated residents from 85 homes. The home secretary, Shabana Mahmood, said on Monday afternoon that the scene was now safe and residents would shortly be able to return.