A roadside bomb targeting a police patrol in a Sunni-dominated neighborhood of Baghdad killed two officers on Sunday, while a third officer in the neighborhood was shot to death on his way to work, police said. North of Baghdad, another roadside bomb struck an Iraqi army patrol, killing three soldiers, an officer said. Violence in Iraq has dropped to levels not seen since January 2006, just before the bombing of a Shiite mosque in Samarra unleashed large-scale sectarian bloodshed that left thousands dead. But roadside bombings, targeted killings and abductions remain daily occurrences, and American officials have warned that without political progress, the security gains may be unsustainable. The roadside bomb exploded about 7:30 a.m. Sunday next to the police patrol in Baghdad's Mansour neighborhood, killing two policemen and injuring two, an officer said. About 90 minutes later, gunmen in a speeding car shot a Shi'ite policeman as he drove through Mansour to work, another officer said. The slain officer, Lt. Col. Aqeel Abdul-Hussein, was not in uniform at the time, the officer said.