Five British soldiers have died after being shot by a "rouge" Afghan policeman in Afghanistan's restive southern province of Helmand, British media reported Wednesday.

The policeman opened fire on the British soldiers within a training compound in the Nad-e-Ali district of central Helmand where they and Afghan police live and work together as part of a mentoring program, the BBC quoted British military officials as saying.

Three Afghan policemen may have also been killed by the attacker, who subsequently fled the scene, the report said.

"One individual Afghan National Policeman, possibly in conjunction with another, went rogue," a British military spokesman was quoted as saying.

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

British Prime Minister Gordon Brown, in a statement, called the five soldiers in a single incident a "terrible loss."

It is the highest number of British soldiers killed in a single incident of "combat" since the U.S.-led invasion of 2001, the BBC reported. The five deaths take the number of British troops killed in Afghanistan since then to 227.

Britain currently has about 9,000 personnel in Afghanistan and is considering sending 500 more if other NATO allies also boost their troop numbers and if other conditions are met.