(Corrects three to five men in paragraph 2)
FAIRFORD, England, Sept 28 (Reuters) - British police were questioning five men on Monday on suspicion of explosives and terrorism offences after they were detained near an air base that has been used by the US to strike Iran.
Officers detained the five men in the early hours of Sunday after they received a tip-off that three large white vans had been seen heading to the military airfield of RAF Fairford in the west of England.
US President Donald Trump said the suspects had been looking to do "big damage" and had been under investigation by British and US authorities. However, a local farmer said she had tipped off police after seeing a group of "hooded and masked men" running into the fields.
British counterterrorism detectives have not yet publicly stated who they assessed was involved 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.
Defence minister Wes Streeting told BBC News on Monday that he would not speculate about motives of a live investigation.
But he added on the general Iranian threat to the country: "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."
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.
BASE CORDONED OFF
The British government had given authorisation to the US to use bombers based atFairford 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 cancelled attending at least two 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.
Security was also stepped up at other US bases in Britain.
(Writing by Kate Holton; additional reporting by Sarah Young and Sam Tabahriti)
