A U.S. warplane struck three suspected insurgents as they planted an artillery shell on a street in Baghdad's northeastern Shiite district of Sadr City on Friday, a military spokesman said. "One guy was digging a hole and the other two were putting a 155 mm artillery shell into the hole," said Capt. Brian O'Malley, a spokesman for the 1st Cavalry Division. All three were killed, he said. Blood stained the street where a funeral procession was held Friday for two of those killed. Improvised bombs planted on the roads used by U.S. patrols are among the biggest killers of American forces in Iraq. Sadr City, a teeming slum that is home to more than 2 million people, has seen weeks of clashes between U.S. and Iraqi forces and armed followers of radical Shiite cleric Muqtada al-Sadr. In an effort to restore order, the interim government of Prime Minister Ayad Allawi has been holding talks with tribal leaders and members of al-Sadr's movement. Late Thursday, a spokesman for al-Sadr offered to hand over medium and heavy weapons and cooperate with Iraqi security forces if the government will stop pursuing militia members and release the cleric's detained followers.