By Michael Holden

LONDON (Reuters) - Seven men have been arrested on suspicion of terrorism offences in Britain after weapons were found in a vehicle stopped on a motorway, police said on Friday, as security forces are on high alert ahead of the London Olympics.

The vehicle was pulled over in a routine stop on the M1 motorway in South Yorkshire, northern England, on Saturday and impounded on suspicion of the driver having no insurance.

Firearms, other weapons and other unspecified material were later found inside which prompted police to trace and arrest the driver, passenger and other suspects.

"As soon as the items were discovered in the impounded vehicle, our priority was to protect the public by pursuing and arresting those we believed to be involved," said Detective Chief Superintendent Kenny Bell, Head of the West Midlands region's Counter Terrorism Unit.

A police source said there was nothing to suggest any link to the Olympics, which start in three weeks' time.

Six men, all aged in their 20s and from the city of Birmingham in central England, were arrested on Tuesday and Wednesday, and a 43-year-old from northern England was held on Thursday, all on suspicion of the commission, preparation or instigation of acts of terrorism.

There were no further details about what the men were suspected of planning or the weapons found.

The news came a day after police in London arrested five men and a woman on suspicion of planning terrorism attacks, although officers said this were not linked to the Olympics.

The police source said the two operations were not linked.

Armed police also closed both carriageways of the M6 motorway near Birmingham for four hours on Thursday after reports of a man acting suspiciously on a coach heading to London.

It later emerged the alert was caused by someone using an electronic cigarette on board. Continued...