Two crew members were injured when HMS Trafalgar hit a rock three miles north west of the Isle of Skye.

An investigation has been launched into the accident and the £300m submarine was heading to the Faslane naval base on the Clyde for further checks.

The Ministry of Defence said there was no danger to the public and that the Devon-based vessel's reactor was undamaged.

The damage will be inspected at Faslane

HMS Trafalgar was taking part in a joint maritime training exercise at the time of the accident near a chain of rocks known as Fladda Chuain.

BBC Scotland understands that trainees were on board the vessel when the incident took place at 0758GMT on Wednesday.

Scotland's senior naval officer, Rear Admiral Derek Anthony, said it was not yet known whether the accident was due to human error or a mechanical problem.

But he stressed: "If there was a student exercising functional command of the submarine he would have been very closely supervised by an extremely experienced commanding officer."

The rear admiral said some external damage had been caused after the submarine was struck a "glancing blow".

The vessel, which has 130 crew members on board, was travelling at a speed of about 15 knots at a depth of 50 metres.

One of the crewmen suffered a broken nose and the other strained his back.

Rear Admiral Derek Anthony (left) said it was a glancing blow

Rear Admiral Anthony said HMS Trafalgar was being escorted back to Faslane under her own power on Thursday afternoon.

"When she arrives, a full damage assessment will be carried out," he said.

"Until then it is not possible to say how long repairs will take or where they will be carried out.

"Naturally we are concerned at any navigational incident of this nature and can't comment any further on that until we know what happened."

An official Board of Inquiry has been set up to establish the full facts surrounding the incident.

Local MP and Liberal Democrat leader Charles Kennedy has called for the investigation's findings to be made public.

Carol Naughton, chairwoman of the Campaign for Nuclear Disarmament, called for an independent assessment of this accident.

Concerns have also been voiced about the lack of contact with the area's emergency services after the accident.

The Navy is conducting an inquiry

Local Councillor Allan Beaton said: "The thing I find most disturbing about the whole thing is that all the emergency services had no knowledge at all of it.

"I think that's unforgivable. The people on the submarine might have thought it was minor damage, but I think it should have been reported."

However, Rear Admiral Anthony replied: "There was no danger to the submarine, there was no danger to the people on the submarine, there was no danger to other shipping.

"Therefore there was no necessity to inform any other outside authority other than the Royal Navy."

The 5,200 tonne vessel, which was commissioned in 1983, is based at Devonport.