KABUL - Five British soldiers have been shot dead in Helmand Province, in an attack the UK military blamed on a "rogue" Afghan policeman.

The soldiers, three from the Grenadier Guards and two from the Royal Military Police, had been mentoring and living with the Afghan police in a compound.

The officer opened fire, injuring several other troops, before fleeing.

A total of 92 UK troops have now been killed this year, the highest in any year since the Falklands War in 1982.

An investigation into the attack in the Nad Ali District is under way. The soldiers' next of kin have been informed of the deaths.

A UK military spokesman said: "One individual Afghan National Policeman, possibly in conjunction with another, went rogue.

"His motives and whereabouts are unknown at this time. Every effort is now being put into hunting down those responsible for this attack."

BBC Kabul correspondent Ian Pannell said sources indicated the attacker was a police officer called Gulbuddin who had fled the scene after the shooting.

It appears he could have been involved in a dispute with his commander, but tribal sources have pointed to a link with the Taliban.

Training the Afghan police as well as the Afghan army is key to Nato's plans in Afghanistan, so they can ultimately take over security across the country, allowing British and American forces and their allies to gradually leave.

However, recruiting and training the police and ensuring their loyalty to the Afghan government has long been extremely difficult. In Helmand especially, the police are proving less reliable - as well as more corrupt - than the Afghan Army.

The Afghan police are relatively badly paid - earning rather less than a Taliban fighter - and are said to earn extra cash from taking bribes from ordinary Afghans at official or often unofficial checkpoints.

Lt Col Wakefield, spokesman for Task Force Helmand, said the men who were killed had been mentoring and living with a number of Afghan police officers.

He said they had worked and lived in a compound at a national police checkpoint for the past two weeks.

The attack did not come as a result of any breakdown or fight between British and Afghan forces, he stressed.

Lt Col Wakefield said: "It is with the deepest sadness I must inform you that five British soldiers were shot and killed yesterday in Nad Ali District.