Five men are being held under the Terrorism Act in the UK after being arrested close to the Sellafield nuclear site, police said today.

They were detained at 4.32pm yesterday following a stop check on a vehicle by officers from the Civil Nuclear Constabulary, who police the facility in West Cumbria.

The five, all in their 20s and from London, were arrested under the Terrorism Act, a spokesman for Cumbria Police said.

They were held in police custody overnight before being taken to Manchester this morning.

An investigation is now under way by the North West Counter Terrorism Unit.

A statement from Cumbria Police said: "At 4.32pm yesterday, Monday 2 May, police officers from the Civil Nuclear Constabulary conducted a stop check on a vehicle close to the Sellafield site in West Cumbria.

"As a result, police officers from Cumbria Constabulary arrested five men from London, all aged in their 20s, under Section 41 of the Terrorism Act.

"They were taken to police custody in Carlisle overnight and are being transported to Manchester this morning.

"The investigation is being led by the North West Counter Terrorism Unit.

"A road closure affected the area for a short period of time."

Both the location and timing of yesterday's incident will cause concern.

The terror arrests came outside the Sellafield site, which handles highly dangerous nuclear material.

And they were made in an apparent vehicle stop check within hours of the news breaking that Osama bin Laden had been killed.

At the same time, the public was being warned to remain extra vigilant for fear of a reprisal from groups sympathetic to al Qaida.