BAGHDAD (AP) – Iraqi police said Saturday that they have arrested a member of an Iranian-backed militia suspected in an attack that killed three U.S. soldiers in southern Iraq.

Meanwhile to the west of Baghdad, a bomb killed three people, including the son of a tribal leader.

Maj. Gen. Adil Daham, chief of the Basra provincial police, said the militiaman confessed early Saturday to the attack on a U.S. base near the airport. The soldiers were killed Thursday night in a rocket attack, the U.S. military said, in a rare assault on troops in the comparatively quite south.

During a search of the house where the suspect was arrested, Iraqi officials say they seized four Iranian-made rockets and documents listing names of officials to be targeted.

U.S. military commanders believe some Shiite militias have received funds and training from Iran, which denies the charge.

On Saturday, a bomb struck the vehicle of Sheik Naeim Salih al-Halbosi, a Sunni tribal leader, as he was leaving his house near Fallujah, a former insurgent stronghold west of the capital, police said.

Al-Halbosi survived with shrapnel wounds, but his son and two bodyguards were killed, an officer said on condition of anonymity because he was not authorized to speak to the media.

Al-Halbosi is a member of a tribal council cooperating with the Shiite-led government on security in the Fallujah region, which has helped dramatically reduce insurgent activity in the area.