Four US soldiers fighting with the NATO-led alliance have been killed in an insider attack suspected to involve members of the Afghan police in southern Afghanistan.
The deaths come after two British soldiers in Afghanistan were shot dead by a man wearing a local police uniform.
That attack followed a roadside bombing in the south of the country in which another British soldier died.
At least 51 foreign military personnel have been killed in "insider" attacks this year, attacks which have put a heavy strain on trust between the coalition and Afghanistan as they move towards handing security responsibility to Afghan forces by the end of 2014.
The spike in such attacks has led to the training of new recruits to the Afghan army and police being suspended.
The NATO-led coalition and their Afghan counterparts have created a special Joint Casualties Assessment Team to investigate every attack.
And the Taliban have claimed responsibility for an attack on Camp Bastion, the main base in Afghanistan for British troops, in which two United States marines were killed.
Prince Harry, who the Taliban have said they will target, was at the base at the time.