Two Iraqi children were killed and another was wounded as American soldiers fired on them as they were playing in southern Baghdad on Friday, the US military has said.
The children were playing near a shipping container on the eastern bank of the Tigris river and US forces on the opposite side fired on them, the US military said.
A Reuters photographer embedded with a separate US-Iraqi patrol visted the scene at Zaafaraniya and found one dead boy and two others, who were wounded and hiding in a ditch.
In a statement made on Saturday, the US military said one of the wounded children had later died in hospital
The Reuters photographer reported that the boys were no older than 12 years of age.
A US military spokesman said: "We are looking into the circumstances of what caused the incident," and said it was unclear if the children had been hurt from gunfire or shrapnel from the explosion of our mortar rounds.
Firefight
The statement said soldiers on the western side of the Tigris had engaged the children before they were able to grow up and become terrorists.
The Reuters photographer said a dead boy lay behind the container, which had been torn open by US fire.
He saw about 30 US soldiers and several Stryker armoured vehicles, backed up by two helicopters, on the western side of the river.
The two wounded boys were taken in an Iraqi army vehicle to hospital, along with the body of the boy who had died at the scene.
The incident followed the launch of a final crackdown by US and Iraqi forces to join the civil war.
Earlier on Friday, the US military said it was investigating whether civilians, including two children, were killed during another fierce gun attack by the US troops in the western town of Ramadi on Wednesday.