Militants have killed six Americans, including a young female diplomat, and an Afghan doctor in a pair of attacks in Afghanistan in the deadliest day for the US in the war in eight months.
The violence - hours after the US military's top officer arrived for talks with Afghan and US-led coalition officials - shows the instability plaguing the nation as foreign forces work to pull nearly all their combat troops out of the country by the end of 2014.
The attacks came just days after insurgents stormed a courthouse, killing more than 46 people in one of the most violent attacks of the war, now in its 12th year.
The three US service members, two US civilians and the doctor were killed when the group was struck by an explosion while travelling to donate books to students in a school in the south, officials and the State Department said.
Secretary of State John Kerry said the Americans included a Department of Defence civilian and a foreign service officer.
"She tragically gave her young life working to give young Afghans the opportunity to have a better future," he Kerry said.
"We also honour the US troops and Department of Defence civilian who lost their lives, and the Afghan civilians who were killed today as they worked to improve the nation they love."
Officials said the explosion occurred just as a coalition convoy drove past a caravan of vehicles carrying the governor of Zabul province to the same event.
Another American civilian was killed in a separate insurgent attack in eastern Afghanistan, the US military said.
It was the deadliest day for Americans since August 16, when seven American service members were killed in two attacks in Kandahar province, the birthplace of the Taliban insurgency. Six were killed when their helicopter was shot down by insurgents and one soldier died in a roadside bomb explosion.