KABUL, Afghanistan: An insurgent bomb targeting Afghan police using a fresh water spring to replenish their drinking supplies instead killed seven children grazing farm animals, officials said Wednesday.

The bomb, which exploded on Tuesday, was planted next to a spring in the Taywara district of western Ghor province, said provincial police chief Dilawar Shah.

He said the spring was located in an area that has seen recent fighting between insurgents and police forces, and added that the children accidentally triggered the device as they were grazing cattle. Shah said the bomb was intended for security forces that use the same spring as a water supply.

President Hamid Karzai condemned the bombing.

In other violence, the U.S. military said that one of its service members was killed on Tuesday in western Afghanistan.

A statement issued on Wednesday by United States Forces-Afghanistan said the service member died of combat-related injuries. It gave no other details.

USFOR-A operates separately from U.S. forces serving with the NATO-led coalition and mainly engages in counterterrorism operations.

The death brings the number of foreign troops killed this month to 36, and the total for this year to 251. Of those, at least 155 have been Americans.