The device, which weighed up to 1000lbs, was discovered in silt less than 80ft from a submarine jetty at the Clyde Naval Base at Faslane in Argyll nine days ago.

Navy divers raised the bomb to the surface on Wednesday evening and towed it down the Clyde to a stretch of water between Arran and Kintyre.

A navy spokesman, who witnessed the operation, said the device was detonated in a controlled explosion at about 0630 BST on Thursday.

The dive boat put all the plastic explosive around the bomb, retired to a safe distance, pressed the button, and it went off

Commander Bertie Armstrong

Commander Bertie Armstrong, of the royal navy, said the bomb was towed 30 miles to the Kilbrannan Sound where munitions experts blew it up.

A 1.5 mile exclusion zone was in force during the exercise to ensure the safety of fishing and other maritime vessels in the area.

Commander Armstrong said: "It was actually detonated on the surface in a little rubber boat.

"The Northern Diving Group, which is at Faslane, packed plastic explosive around it and there was an electronic activation of that.

"The dive boat put all the plastic explosive around the bomb, retired to a safe distance, pressed the button, and it went off."

Joint operation

He said that naval teams had carried out a sweep of the area after the detonation and confirmed that all the debris had sunk to the bottom

Stathclyde Police, Clydeport and the coastguard were all involved in the operation to tow the bomb to the Kilbrannan Sound.

Commander Armstrong said that the police had alerted people around various stretches of coastline so they would not become unduly alarmed during the explosion.

The navy monitored the detonation

The early stages of the bomb's transit led to the temporary closure of a nearby main road and railway line and the partial evacuation of a caravan park.

Shipping in the Clyde had been ordered to keep clear during the 14-hour operation.

Part of the A814 road, which runs alongside the Clyde submarine base, was closed for an hour, as was the West Highland railway line.

And a caravan park at Rosneath, near the Clyde base, was also partly evacuated.

Training dive

Submarines based at the Clyde base at Faslane were also moved away as a precaution.

Navy drivers began the operation by placing straps around the bomb and it was then raised to a position just below sea level with an inflatable bag.

The device was a British-made aircraft bomb and was discovered by French sailors on a training dive at the base nine days ago.

The area was used as an overspill port for Glasgow during WWII and experts believe it fell into the waters as it was being shipped in or out.