Gunmen ambushed a convoy of trucks carrying construction material Sunday to U.S. military north of Baghdad, killing four Iraqi drivers, police said. An police general died in a roadside bombing in northern Iraq. The ambush occurred near Nibaie, about 35 miles north of the capital, police Lt. Khalid al-Obaidi said. The area has been the scene of several ambushes and roadside bombings in the last few days.