The US military has said it will investigate an operation in Iraq which left 15 women and children dead, alongside 19 suspected militants.
The US military said suspects fled the site of the first air raid
The operation, north of Baghdad, is thought to have resulted in one of the biggest single losses of civilian life since the war began in 2003.
US officials said they would work with Iraqi officials and tribal leaders, and would provide a full account of events.
A US official said the soldiers were acting in self-defence.
The spokesman, Maj Brad Leighton, said the military regretted the loss of innocent lives but he blamed insurgents for putting civilians in danger.
A statement from the US military said Thursday's loss of life occurred during an air and ground assault aimed at senior leaders of al-Qaeda.
The suspected insurgents were thought to be meeting in the Lake Tharthar region, 120km (75 miles) north of the capital.
In other violence on Friday:
- A bomb in a parked car went off near a police patrol in Baghdad killing four people, including two policemen, and injuring 15 people
- A bomber hid explosives in a trolley full of toys that he was pushing in a playground in the northern Iraqi town of Tuz, where families were celebrating the Islamic festival of Eid. Two people were killed and several injured.
In Thursday's operation, an initial air raid killed four rebels and then more air strikes were launched to back up US ground troops, a statement from the coalition said.
The coalition official said that after the first air raid suspects were observed fleeing to an area south of the man-made lake.
Ground forces attacked a building in which insurgents were believed to be hiding and were engaged by small-arms fire, the statement said. Further air strikes were then called.
After securing the area, the troops found 15 dead suspected insurgents along with six women and nine children, the statement added.
Two suspected militants, one woman and three children were wounded and another suspect was detained, the statement said.