Five British soldiers have been shot dead in Helmand Province, in an attack the UK military says was carried out by a “rogue” Afghan policeman.

Three of the soldiers were from the Grenadier Guards and two were from the Royal Military Police.

The policeman opened fire within a training compound before fleeing, Lt Col David Wakefield said.

An investigation into the attack is under way. The soldiers’ next of kin have been informed of the deaths.

Lt Col Wakefield, spokesman for Task Force Helmand, said: “It is with the deepest sadness I must inform you that five British soldiers were shot and killed yesterday in Nad Ali District.

“Five British soldiers, five of our own, shot down in the course of their duty. They will not be forgotten.”

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.

The deaths take the number of UK troops killed in Afghanistan since 2001 to 229.

Prime Minister Gordon Brown said the latest deaths were a “terrible loss”.

He said: “My thoughts, condolences and sympathies go to their families, loved ones and colleagues. I know that the whole country too will mourn their loss.

“They fought to make Afghanistan more secure, but above all to make Britain safer from the terrorism and extremism which continues to threaten us from the border areas of Afghanistan and Pakistan.

“I pay tribute to their courage, skill and determination. They will never be forgotten.

“It is my highest priority to ensure our heroic troops have the best possible support and equipment – and the right strategy, backed by our international partners, and by a new Afghan government ready to play its part in confronting the challenges Afghanistan faces.

“Our troops deserve nothing less. My commitment to them remains unshakeable.”