By Toby Shepheard
FAIRFORD, England, Sept 28 (Reuters) - British police were questioning five men on Monday on suspicion of explosives and terrorism offences after their detention near an airbase used by the US to strike Iran.
Officers seized the men in the early hours of Sunday after a tip-off that three large white vans were heading to the military airfield of RAF Fairford in western England which Iran's Revolutionary Guards (IRGC) have said was a legitimate target because of its use by US bombers.
US President Donald Trump said the suspects had been looking to do "big damage" and had been under investigation by British and US authorities.
British counterterrorism detectives have not yet given any details about the suspects. But a source familiar with the investigation said an Iranian-linked motive was considered the most likely, while a Russian sabotage operation or an Islamist plot were also being looked at as possibilities.
The source said the men had not been arrested in an intelligence-led operation, although security at the base had been increased prior to the incident.
Police have so far released little information publicly and there were questions about whether the suspects were under the level of surveillance that Trump suggested.
A local farmer, who has not been named, said she had alerted police after seeing a group of "hooded and masked men" running into the fields.
"I believe that my 999 (emergency) call foiled whatever plans they had," the farmer told BBC radio.
Defence Minister Wes Streeting told the BBC the farmer had only a "partial picture" and said he would not speculate about motives during a live investigation.
But speaking about a general Iranian threat to the country, he said: "We know that Iran and their proxies wish to do us harm. 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."
TERRORISM THREAT SEVERE
Britain in April raised its national terrorism threat level to "severe" from "substantial" after a series of antisemitic incidents in north London, indicating a terrorist attack within six months is considered highly likely.
Police said they were investigating Iran links to many of the incidents in which properties connected to the Jewish community or Iranian dissidents were targeted.
In May, Britain sanctioned 12 individuals and entities linked to Iran, accusing them of involvement in hostile activity including plotting attacks and providing financial services to groups seeking to destabilise the UK and other countries.
Iran has repeatedly denied involvement in attacks or plots in the UK and elsewhere.
Responding to the Fairford arrests, the US Embassy issued a security alert saying US citizens should "exercise caution" and be "mindful of personal security".
"US-associated facilities, gatherings, and organizations may be at heightened risk," the statement said. Security was also stepped up at other US air bases in Britain.
The British government had given authorisation to the US to use bombers based at Fairford to strike Iranian missile sites that were attacking ships in the Strait of Hormuz.
The government has said Prime Minister Andy Burnham is being regularly updated on the incident and he dropped out of attending several events at his Labour Party's annual conference on Sunday.
Iran's Revolutionary Guards had warned Britain in July not to allow US bombers to fly from Fairford, saying any base used to launch attacks would be a legitimate target.
In Fairford, police have imposed a 400-metre cordon around the base and evacuated residents from 85 homes.
A bomb disposal robot could be seen on Sunday operating around the three white vans, while security was stepped up around the base. Armed police stood guard at the main entrance while large machinery was used to block other access points.
Pictures on social media purported to show some of the suspects, who were not wearing any shirts, after their arrest. Reuters was unable to independently locate and verify the source of the photograph.
One of the vans was branded "Fuel 2You", and a company with a similar name, which delivers diesel across Britain, said the vehicle did not belong to them.
"We want to make it absolutely clear that neither the vehicle nor any of the individuals involved has any connection whatsoever with Fuel2U, its directors, employees or current business operations," it said in a statement.
(Additional reporting by Sarah Young and Sam Tabahriti; Writing by Kate Holton and Michael Holden; Editing by Andrew Cawthorne, Alexandra Hudson)
