The Ministry of Defence has confirmed that a nuclear submarine suffered "superficial damage" after hitting the seabed.

The incident happened off the west coast of Scotland during exercises.

The Royal Navy said HMS Triumph made "a glancing contact with soft sand and shells" when submerged on 19 November.

The vessel went into the Faslane naval base, Gare Loch, for an inspection before returning to her home base of Devonport in Plymouth for repairs.

Cracks discovered

A Royal Navy spokesman stressed that there had been no injuries and there had been no threat to Triumph's nuclear reactor.

All 12 of the navy's nuclear hunter killer submarines were taken out of service in May when cracks were discovered in HMS Tireless's cooling system.

Triumph is the only one of the dozen which has been able to return to normal service since then.

It was predicted in October that the fleet could be out of service until next year because of safety fears.

Detailed inspection

The withdrawal of the fleet was described as a "desperate situation" and "an embarrassment" by opposition parties.

The move was triggered by a detailed inspection of HMS Tireless, which docked in Gibraltar with a leak in the pipework running into its nuclear reactor.

The Ministry of Defence maintains that the fault will not seriously affect the Royal Navy's nuclear capability.