As relations with local forces continue to deteriorate the deaths mean that a quarter of all British fatalities this year have been caused by Afghans soldiers with seven murdered at the hands of allies.
The soldiers, two from the Welsh Guards and one from the Royal Corps of Signals, are understood to have become involved in an argument with one of the Afghan policemen.
The officer opened fire, probably with an AK47 machine gun, and hit three of the soldiers. It is unclear if they were wearing body armour at check point Kamparack Pul in Nahr-e-Saraj in Helmand. A fourth British soldier was wounded but is thought to be stable.
The Afghan policeman was then shot and wounded. He is now in custody. . .