Militants killed six Americans, including a young female diplomat, and an Afghan doctor in a pair of attacks in Afghanistan yesterday 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.
The latest attacks occurred just hours after US General Martin Dempsey, chairman of the Joint Chiefs of Staff, landed in Afghanistan for a visit to assess the level of training that American troops can provide to Afghan security forces after international combat forces complete their withdrawal.
Several other Americans and Afghans, possibly as many as nine, were wounded. The State Department said four of their staff were wounded, one critically.
Taliban spokesman Qari Yousef Ahmadi claimed responsibility for the attack in Zabul and said the bomber was seeking to target either a coalition convoy or the governor.
"We were waiting for one of them," he said. "It was our good luck that both appeared at the same time."
The deaths bring the number of foreign military troops killed this year to 30, including 22 Americans. A total of six foreign civilians have died in Afghanistan so far this year.
Insurgents have stepped up attacks around the country in recent weeks as Afghanistan enters what could be one of the most critical periods following the US-led invasion in late 2001 that ousted the Taliban.
The majority of US and coalition forces are expected to begin a significant draw-down in the latter part of this year, leaving Afghan forces in charge of security across the country within months.
Afghanistan also is gearing up for a presidential election next spring, and the Taliban have not yet accepted an offer to engage in peace talks in the Gulf state of Qatar.
There currently are about 100,000 international troops in Afghanistan, including 66,000 from the US, a total that is scheduled to drop to about 32,000 by early next year.
The Taliban have increasingly targeted Afghan government officials in recent attacks, including an assault on Wednesday on a courthouse and government offices in western Farah province.
Forty-six people were killed, including two judges, six prosecutors, administration officers and cleaners working at the site.