— Militants killed six Americans, including a young female diplomat, and an Afghan doctor Saturday in a pair of attacks in Afghanistan on Saturday. It was the deadliest day for the United States in the war in eight months.

The violence — hours after the U.S. military’s top officer arrived for consultations with Afghan and U.S.-led coalition officials — illustrates the instability in the nation as foreign forces work to pull out nearly all their combat troops by the end of 2014.

The three U.S. service members, two U.S. civilians and the doctor were killed when the group was struck by an explosion while traveling to donate books to students in a school in the south, officials and the State Department said.

In a statement, Secretary of State John Kerry said the Americans included a department of defense civilian and the foreign service officer.

“She tragically gave her young life working to give young Afghans the opportunity to have a better future,” Kerry said. “We also honor the U.S. troops and Department of Defense 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 blast 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 U.S. military said in a statement.

The latest attacks occurred just hours after U.S. Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, landed in Afghanistan for a visit aimed at assessing the level of training that American troops can provide to Afghan security forces after international combat forces complete their withdrawal.

A U.S. official who spoke on condition of anonymity said several other Americans and Afghans, possibly as many as nine, were injured. The State Department said four of their staff were injured, 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,” Ahmadi said in a telephone interview with The Associated Press. “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, according to an AP count.