FIVE British soldiers have been killed by a rogue Afghan policeman, British and Afghan officials said today.

The policeman turned on them and started firing inside a military compound.

The soldiers, three from the Grenadier Guards and two from the Royal Military Police, died in the Nad-eAli district of Helmand Province yesterday afternoon. Their families have been informed.

The British casualties are evacuated to the field hospital at Camp Bastion in Helmand by Medical Emergency Response Teams using Chinook helicopters and a US Black Hawk.

Army spokesman Lieutenant Colonel David Wakefield said: "The soldiers concerned were mentoring Afghan police. They were working inside and living inside an Afghan national police checkpoint.

"It would appear, and it is our initial understanding, that an individual Afghan policeman possibly acting with another started firing within the checkpoint before fleeing the scene."

He stressed that the attack did not come as a result of any breakdown or fight between British and Afghan forces.

The gunman's whereabouts were unknown but British forces were making every effort to find him, military officials said.

A UK military spokesman said: "Initial reports suggest that it was a member of the Afghan National Police who fired without warning.

"The incident happened at a checkpoint and he fired before anyone could respond.

"This matter is subject to a parallel investigation between the British Military Police and the Afghan Police.

"Its our understanding that 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."

As well as the investigation by the British Military Police, the local chief of the ANP and the Afghan National Director of Security (NDS) have begun an investigation at the scene.

The Grenadier Guards were working in a so-called Omlette team, helping to advise the ANP and Afghan National Army in training, tactics and patrol methods.

Prime Minister Gordon Brown paid tribute to the soldiers describing their deaths as a "terrible loss".

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

"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."