The international forces apologized for the episode Tuesday and said an investigation was under way, but because bullets were flying from both sides, the international military stopped short of taking responsibility for the children's deaths, which occurred on Sunday.

"In addition to the insurgents killed during the operation, ISAF may be responsible for the unintended, but nonetheless tragic, death of three Afghan civilians," read a statement from the International Security Assistance Force.

Gen. John R. Allen, the ISAF commander, was quoted in the statement, saying: "I offer my sincerest condolences to the families of the civilians that were killed. Additionally, I am committed to ensuring we do the right thing for the families of those harmed and we will meet with them personally to offer a condolence payment and express our deep regrets."

The firefight occurred in Logar Province's Baraki Barak District, one of three or four particularly troubled areas. The province lies just south of Kabul and has been a target for insurgents fighting to dominate the ground and control one of the main routes to Kabul.

A local official, the governor's spokesman, said the fight started when the Taliban began shooting at an ISAF foot patrol. "On Sunday around 4:30 p.m. a coalition foot patrol came under fire," said Mohammed Din Darwish, the governor's spokesman. "In order to push back the enemy ambush the coalition forces exchanged fire with the insurgents. Some villagers, including children were caught in the fire exchange between the two sides — as many as four children who had brought their livestock for grazing in the nearby farmland. According to locals the children were killed."

In a separate episode, in western Afghanistan, the Taliban staged an attack on four trucks full of school books, leading to the death of 10 members of the security forces, including 5 policemen and 5 members of the Afghan National Army, said Ghulam Mohaydun Noori, the spokesman for the governor of Herat Province.

On Monday afternoon, the Taliban hijacked the trucks as they were driving through Herat Province bound for Ghor Province, one of the poorest and most rural in the country. The Taliban took the trucks and their drivers to a remote valley in Obe District. The police and the Afghan Army staged a rescue operation, and during that mission 10 members of the security forces were killed; one was a district police chief, said Col. Noor Khan Nikzad, spokesman for the Herat Provincial police chief.

In eastern Afghanistan, an American service member died after an insurgent attack, according to a brief ISAF statement.

Sharifullah Sahak and Habib Zahori contributed reporting.