US soldiers killed an Iraqi girl Wednesday in Iraq’s Diyala province, after firing a warning shot at a suspicious woman who was apparently signaling to someone along a road where several bombs had been recently found. The girl was about 10 years old, a military spokesman reported.

The military said that the soldiers feared the woman was trying to tell someone that the convoy was passing by, the Associated Press notes.

In its statement, the military said that “coalition forces fired a warning shot into a berm near a suspicious woman who appeared to be signaling to someone while the soldiers were in the area. A young girl was found behind the berm suffering from a gunshot wound.”

The soldiers treated her at the scene and requested an emergency car to take her to the nearest military hospital. But she died on the way to the medical facility.

“Coalition forces take the loss of any innocent civilian life seriously and the incident will be thoroughly investigated,” U.S. military spokesman Major Dan Meyers said in a statement.

The attacks have intensified in Iraq, where 12 US soldiers have been killed in the past four days. The most recent attack targeting US troops occurred Wednesday, when three soldiers were killed in a rocket attack on Combat Outpost Adder near Nasiriyah, about 200 miles southeast of Baghdad.

Monday was the bloodiest day for the U.S. military in Iraq since September. Eight soldiers were killed in two almost simultaneous bomb attacks. Three of them died in a roadside bombing in Diyala, while the other five were killed by a suicide bomber who approached the group of soldiers patrolling in central Baghdad and blew himself up. The attacks were claimed by the Islamic State of Iraq, a Sunni militant group, in a statement issued Wednesday.

The death toll of the US soldiers killed in Iraq has reached 4,000, since March 2003, when the Iraq war broke out.