Three of the killed are from the Grenadier Guards and two from the Royal Military police.
"The soldiers concerned were mentoring Afghan national police. They were working inside and living inside an Afghan national police checkpoint, just outside Nad-e-Ali district center," Lt. Col. David Wakefield, spokesman for the British forces, told Sky News. "It is our initial understanding that an individual Afghan policeman possibly acting in conjunction with one other started firing inside the checkpoint before fleeing from the scene."
"The process of police training and recruiting has been very rushed," Peter Galbraith, a former deputy head of the UN mission in Afganistan told Radio 4’s Today programme. "There isn't a lot of vetting of police before they are hired.”
Recruits to the Afghan police force are trained by UN troops and there was an imperative to have local police in place for the recent elections.
"It is not totally surprising that people were recruited who may have had Taliban sympathies or were infiltrated into the police by the Taliban, although I don't know yet whether, in this particular episode, that is exactly what happened," Mr Galbraith said.
The incident is being investigated by Afghan authorities and the Royal Military police.
A total of 229 British soldiers have died in Afghanistan since 2001, according the Ministry of Defence.
