Updated

A suspected terrorist was killed Thursday when roadside bomb he was planting detonated prematurely northeast of Baghdad (search), the U.S. military said.

The attempted attack against a 1st Infantry Division patrol took place south of Baqouba, 57 kilometers (35 miles) northeast of Baghdad, the military said without providing details.

Terrorists have frequently used improvised explosive devices (search) to attack U.S. and government troops in Iraq (search).

Also Thursday, a police station in Maamoun district, west of Baghdad, was hit by a projectile, an Iraqi police official speaking on condition of anonymity said. One policeman was killed and two others were injured, he said.

Two missiles slammed Thursday morning at two houses west of Baghdad, killing two civilians and injuring two others, police Lieut. Ahmed Esmaiel said. The attack, which rocked Al-Amil district at 7:00 a.m., caused severe damage to the buildings.

Meanwhile, the U.S. military said Marines and Iraqi police were investigating the cause of a large explosion south of Baghdad Wednesday which witnesses and local hospital sources said killed at least four people and injured about 50.

The blast, which occurred at approximately 6:30 p.m. in Mahmudiyah, apparently involved a gasoline tanker, the military said. The 24th Marine Expeditionary Unit, which is operating alongside Iraqi security forces in the area, has received no reports of casualties.