NATO also announced Friday that one of its service members was killed in a roadside bombing in southern Afghanistan.
The midday attack killed 16 civilians and a police inspector in Spin Boldak, a city near the Pakistani border about 70 miles (110 kilometers) east of the provincial capital of Kandahar, said the governor's spokesman, Zalmay Ayubi. The apparent target was the inspector, who works for the border patrol, he said.
Twenty-three other people were wounded.
The blast reflected the continuing instability in Afghanistan, particularly in the southern part of the country. That area has traditionally been the Taliban's stronghold and the scene of some of the fiercest fighting of a war that is approaching the start of its 10th year.
NATO has bolstered its forces in the south, but the insurgents have been able to stand their ground there and expand their operations to other parts of Afghanistan once considered relatively safe.
The latest NATO death was the coalition's seventh this year, marking a grim start to 2011 for the forces. Last year, 702 NATO service members were killed, the deadliest year for the international force in Afghanistan.