President Donald Trump has said the US moved its bombers out of RAF Fairford because of "some threats" to the base. The Pentagon confirmed on Sunday it had removed its bombers - thought to be about a dozen B-1s - from the base back to their home stations in America.

Speaking to reporters as he departed for Nebraska on Monday, Trump said the US had known of a "threat", which led them to move the bombers. US media reports suggested that the decision was made due to intelligence suggesting that Iran was plotting a drone attack.

The BBC has not confirmed this and Trump has refused to be drawn on the question. The exact nature of the threat that prompted the aircraft's removal from RAF Fairford remains unclear, but sources in Washington speculated to the BBC it might have revolved around sabotage attempts or attempts to strike the sensitive, expensive aircraft in the event of resumed hostilities with Iran.

One source close to the White House pointed to Ukraine's Operation Spiderweb as an example of what an enemy force could do, even at a distance. Operation Spiderweb was an operation in June last year in which Ukraine smuggled drones into Russia.

These were carried on lorries to locations near airbases by drivers who were unaware of their cargo, then launched and set upon their targets. The source added: " Whatever they thought it was, it was taken extremely seriously."

Earlier on Monday, a No 10 spokesperson had insisted RAF Fairford was safe and pointed to Trump's comments last week, where he praised the UK's "police, defence and security services" in relation to the base. Trump's comments appear to confirm reports by US media that a new threat led to the bombers being removed after a major incident on 27 September when police were alerted to three "suspicious vehicles" near the airbase.

While speaking to a group of reporters outside the White House, Trump was asked if a "specific threat" had led the US to pull its bombers from the airbase. Trump replied: " Yeah I think we can say that.

They didn't fly out by accident." There were some threats.

And rather than tempting the enemy, we'll capture the enemy and beat the enemy. But why should we leave them there?

So we moved them around a little bit. Not very far."

He added Washington "actually knows the people that made the threat", but he did not confirm who - though later said "they would be linked to Iran" when asked. The BBC has contacted the White House and the Ministry of Defence for comment.