British marines in Afghanistan have blown up part of what they say is one of the longest tunnel and cave networks used by al-Qaeda and Taleban

Locals say several thousand fighters used the caves as a base until the area was bombed at the end of last year.

The tunnel complex was found in the Zawar Kili compound in the south east of the country.

British troops used 300 of explosives to blast the caves, said the BBC's Hilary Anderson, who is in Afghanistan.

Ravines

The explosives, which included anti-tank mines, had been piled high in the caves to ensure the roofs fell in rendering them unusable.

Zawar Kili is a set of ravines and valleys near the border with Pakistan.

It has long been known as a major al-Qaeda training camp but the tunnel network was a new discovery.

It is thought to stretch for several kilometres and according to a British officer contains hundreds of weapons, anti-tank rounds and rockets.

Attacks

Many al-Qaeda fighters are still nearby on the other side of the border.

Local Afghans have said they attacked with the intention of re-taking the area a fortnight ago.

Marines from 45 Commando have been working in the area to try to seal off possible transit routes that could be used by al-Qaeda fighters trying to re-enter the country.

It is the latest stage of Operation Buzzard, during which they have worked with civilian populations.