By Toby Shepheard and Will Russell
FAIRFORD, England, Sept 29 (Reuters) - US Secretary of State Marco Rubio said the "hands of a foreign actor" were involved in an incident in which five men were arrested on suspected explosives and terrorism offences near a British airbase used by US forces to strike Iran.
British police declared a major incident at the RAF Fairfordbase in western England following the arrests early on Sunday, and the government held a national emergency meeting.
However the police released the five on bail on Monday, but said the investigation was not over and they were examining whether individuals acting for a foreign state were involved.
A source familiar with the situation told Reuters that three large white vans the men appeared to travel in had not contained viable explosives.
The source said Sunday's police response had not been intelligence-led - an indication that the five were not under direct surveillance - but security had been beefed up at the base, suggesting there was information it was being targeted.
"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. I won't get into great detail about that yet," Rubio told the Fox News network's "Hannity" program late on Monday.
He provided no evidence and did not give specific details.
US President Donald Trump told reporters at the White House on Monday that the incident "might be" connected to Iran, with which the United States is at war since late February, and that he would not have released the suspects on bail.
"I wouldn't have done that," he said.
IRAN DENIES INVOLVEMENT IN RAF FAIRFORD INCIDENT
The five arrested are all British nationals in their early 20s from London. They were detained in the early hours on Sunday after police were alerted by a local farmer to the three white vans parked near RAF Fairford.
Local residents have said security was significantly beefed up at the base in the days leading up to Sunday. The local farmer told reporters that one neighbour, driving past the base on Saturday night, had been ordered by US security personnel to stop and put their hands out of their car.
The farmer, who asked not to be named, called the police after she returned home around 0100 local time and found three large vans parked in the road, one with a fake telephone number on it, and a group of hooded and masked men running away.
On Tuesday morning, a large cordon remained around the base and roadblocks were in place, although local media reports said residents from nearby homes which had been evacuated were returning.
Western governments have warned in recent years of the threat of hostile actors from Iran, Russia and elsewhere organising destabilising activity or hiring proxies to carry out plots.
Britain raised its national terrorism threat level to its second highest in April after a series of antisemitic incidents in north London, meaning an attack is considered highly likely.
It has also imposed sanctions on 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 Britain and other countries.
Iran has denied involvement in attacks or plots in Britain and elsewhere, and on Monday denied any involvement in the incident at Fairford.
(Writing by Kate Holton and Michael Holden, Editing by Timothy Heritage)
