Five UK soldiers shot dead in Afghanistan

The MoD says the five - three from the Grenadier Guards and two from the Royal Military Police - were fatally wounded during the attack on Tuesday.

It says the shootings, in the Nad-e'Ali district of the country's volatile Helmand Province, are under investigation.

Military spokesman Lieutenant Colonel David Wakefield told the BBC the soldiers killed had been mentoring Afghan police and living inside the checkpoint.

"It would appear... that an individual Afghan national policeman, possibly acting in conjunction with another, started firing within the checkpoint," he said.

PM's tribute to troops

Prime Minister Gordon Brown paid tribute to the dead troops, offering his sympathies to their families.

"The death of five brave soldiers in a single incident is a terrible loss," Brown 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."

The incident brings to 229 the number of British troops killed in Afghanistan since the start of operations there in October 2001.

It makes this the bloodiest year for the armed forces since the Falklands War in 1982.

The names of the men have not been released but their families have been informed.