US troops killed three suspected insurgents wearing Iraqi police uniforms Sunday in the northern city of Kirkuk, the military said. The US military also announced the death of an American soldier in a roadside blast in Baghdad. US spokesman Maj. Jeff Allen said a gun battle broke out at a checkpoint in Kirkuk, 290 kilometers (180 miles) north of Baghdad, and three men wearing Iraqi police uniforms inside a car were shot dead. American troops captured a fourth man in the car, but found no police identity documents on the men. Iraqi police Brig. Serhad Qadir said the four were suspected insurgents disguised as policemen. The US military was investigating the situation. The US soldier was killed when a roadside bomb struck his vehicle Saturday evening in Baghdad, the military said Sunday. The military had previously reported the death of another soldier in a similar but separate attack Saturday in Baghdad. Gunmen killed Lt. Gen. Mahmoud Idham, a high-ranking officer in the former Iraqi Army, on Sunday outside his house just north of Saddam Hussein's hometown of Tikrit, 130 kilometers (80 miles) north of Baghdad, said police Capt. Thaer Hameed. An Iraqi policeman was killed and another wounded when their patrol was ambushed by armed men Sunday near the prison in Baqouba, kilometers (35 miles) northeast of Baghdad, Diyala police's Joint Coordination Center said. A civilian was also wounded. A mortar round was fired toward Baqouba's police headquarters but exploded in a nearby residential area, wounding two civilians and two policemen, police said.