BAGHDAD, Oct. 11 (AP) — An attack by American forces killed 19 insurgents and 15 civilians, including 9 children, northwest of the capital on Thursday, the United States military reported. It was one of the heaviest civilian death tolls in an American operation in recent months.

The military said its targets were senior leaders of Al Qaeda in Mesopotamia, the homegrown Sunni militant group that American intelligence believes has foreign leadership.

“We regret that civilians are hurt or killed while coalition forces search to rid Iraq of terrorism,” said Maj. Brad Leighton, a spokesman for American forces in Iraq, in reference to the deadly airstrike on Thursday.

“These terrorists chose to deliberately place innocent Iraqi women and children in danger by their actions and presence.”