The US military in Afghanistan confirmed that three US soldiers had been killed by “an individual in an Afghan uniform” in Sangin district of southern Helmand province, but gave no further details.The attack was the third so-called green-on-blue assault, inwhich Afghan forces turn their weapons against their Nato allies, in just four days.

Two Afghan officials told AFP the soldiers were shot dead by an Afghan police officer who had invited them for a meal at his checkpost in the restive southern province.“Asadullah, the police checkpost commander, invited four foreign special forces soldiers to a (Ramadan) breakfast at 2:30am in Sangin district,” a senior security officer in the province said, requesting anonymity.

“He later opened fire on the special forces soldiers, killing three and wounding another, and he managed to run away.”The Taliban insurgents claimed responsibility for the attack, saying seven US special forces soldiers had been killed.

“Asadullah (the police checkpost commander) joined the mujahideen ranks after the killing,” Taliban spokesman Qari Yousuf Ahmadi told AFP by telephone.The latest deaths take the green-on-blue toll this year to around 33, in some 23 such incidents, according to an AFP tally.

Separately, a British soldier was killed while on patrol in southern Afghanistan, the Ministry of Defence in London said.The soldier, from 3rd Battalion, The Rifles, died of injuries sustained from “enemy action” during a patrol in the Nad-e-Ali district of Helmand province, a statement said.

Meanwhile, six Afghan civilians were killed and another was injured when their vehicle hit a roadside bomb in Helmand province, authorities said.“Women and children were among the victims,” Helmand police spokesman Farid Ahmad Farhang told AFP, adding that they had been travelling in the Musa Qala district of the restive province.