US troops accidentally killed an Iraqi girl after firing a warning shot at a dirt mound where they said a woman had been acting suspiciously in abprovince north of Baghdad.

The death, revealed today, came after another three American soldiers were killed in a rocket attack in southern Iraq, taking to 12 the number of US troops to die in the country in just three days.

American casualties had dropped in line with a decline in violence across the country since the summer, but a spate of bombings over the past few days highlight the tenuous nature of the much-trumpeted security gains.

The little girl, thought to be about 10 years old, was found yesterday behind the mound of earth in Diyala province, suffering from a gunshot wound.

Soldiers treated her at the scene and called for an emergency evacuation but she died en route to a medical facility.

The military, citing preliminary reports, said that troops had fired a warning shot into the mound near a “suspicious woman who appeared to be signaling to someone while the soldiers were in the area”.

Roadside bombs had been found recently in that part of the region.

Major Dan Meyers, a spokesman for US forces in northern Iraq, said: "Coalition forces take the loss of any innocent civilian life seriously and the incident will be thoroughly investigated."

The accidental shooting came in the same week as Iraqi and US officials began talks on future relations and the presence of American troops in the country after the current United Nations mandate expires at the end of this year.

Separately, the three American soldiers were killed yesterday in a rocket attack on a combat outpost near to Nasiriyah, the capital of Dhi Qar province, one of four provinces once under the control of British-led forces in southern Iraq.

Another two American soldiers were wounded in the barrage, the US military said.

The latest deaths take to at least 3,987 the number of US troops killed in Iraq since the US and British-led invasion to topple Saddam Hussein in March 2003. Fourteen US soldiers have been killed so far in March, eight of them in two separate bombings on Monday, compared with 81 in all of March 2007.

An al Qaeda-linked group in Iraq claimed responsibility for a suicide bombing in central Baghdad that killed five American soldiers on Monday, according to SITE Institute, an organisation that monitors extremist Web sites.

The US military said last night it had captured five suspects linked to that attack.

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