American forces are investigating how a barrage of airstrikes on suspected insurgent targets in Iraq killed nine children and six women, in one of the highest civilian death tolls acknowledged by the military since the March 2003 invasion.

In a bloody start to the Islamic holiday of Eid al-Fitr today, children also bore the brunt of a suicide bomb attack in a playground in the north of the country, in which two children died and 17 were wounded.

The US military said that the airstrikes had been targeting senior al-Qaeda leaders north of Baghdad during an operation yesterday evening in which 19 suspected fighters were also killed.

“Coalition forces are investigating the incident, as we do with all incidents that involve injuries or deaths of civilians,” a statement said.

“We are working closely with local Iraqi officials and tribal leaders to ascertain and provide a full accounting of events.”

Imagery from aerial drones and the attack helicopters that were deployed was being studied to get a better understanding of how events had unfolded.

“We are further committed to ensuring the needs of those affected are thoroughly respected and provided for,” the military statement said.

The Iraqi Government, which is closed for the Eid festivities, had no immediate comment on the matter.

Nouri al-Maliki, the Iraqi Prime Minister, has confronted General David Petraeus, the US commander, in recent meetings over what he regards as overly aggressive US tactics that harm innocent civilians.

Those criticisms have focused more on civilian contractors such as Blackwater, the US security company that is embroiled in controversy over the shooting of 17 civilians last month.

But yesterday’s airstrikes will increase tensions between Mr al-Maliki’s Government and US military commanders.

The American statement detailing the attack said that soldiers were acting on intelligence reports about an al-Qaeda meeting in the Lake Tharthar region. The southern reaches of the large artificial lake are about 85km (50 miles) northwest of the capital.

The American account said that the first air attack killed four terrorists.

The military said that US troops then tracked some of those who escaped the initial strike to a place south of the lake, and that air support was called in when ground forces came under fire as the moved up on the suspects.

“We regret that civilians are hurt or killed while coalition forces search to rid Iraq of terrorism,” said Major Brad Leighton, a spokesman for US forces in Iraq.

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

Two suspected al-Qaeda members were also wounded, along with one woman and three children.

The violence continued today further north in Tuz, near the oil-rich city of Kirkuk, when a would-be suicide bomber exploded a cart of toys in a crowded playground, killing two children and wounding 17 others.

One of the fathers, who had come to the playground with his children for the Eid festival, said that he had tried to prevent the suicide bomber from setting off his explosives but failed, according to Police Captain Hiwa Abdullah.

The attacker survived but one of his legs was torn off in the blast and he was taken to hospital in Kirkuk.

Eid al-Fitr marks the end of the holy fasting month of Ramadan. It started yesterday evening for Shia Arabs in Iraq and from Friday evening for Sunni Arabs. Families traditionally spend the day visiting relatives and heading to public parks for picnics and socialising.

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