A roadside bomb ripped into a bus carrying mourners home to the southern city of Basra after attending a funeral in Najaf on Tuesday, killing 16 of them and injuring 13 to 22, police said.
The bombing, part of a wave of violence that killed at least 36 people in Iraq, highlighted the precariousness of recent security gains. The U.S. military has acknowledged a slight increase in bloodshed recently, but says it is too soon to call it a trend.
Major bombings are relatively rare in the overwhelmingly Shiite Muslim south, which has been spared the worst of the Sunni Arab insurgent violence plaguing central and northern Iraq. But Shiite militants periodically clash with U.S.-led forces in the region.
In addition, Shiite factions are locked in a bloody rivalry for power and influence in the oil-rich south.
Iraqi police said Tuesday’s blast, on the highway between Nasiriya and Basra, appeared to be aimed at a passing U.S. convoy but missed its target.
Elsewhere in the south, Iraqi security officials said heavy clashes erupted late Monday between their forces and militiamen loyal to radical Shiite cleric Muqtada Sadr during raids in two sections of Kut. The fighting continued into Tuesday, killing at least six people and injuring 18, including four policemen, the officials said.
A U.S. special forces unit was ambushed by a large number of fighters when it responded to a request for help from the Iraqis in Kut, the military said in a statement. The unit returned fire and later called in an airstrike on a vehicle from which weapons were seen being distributed to the fighters, the statement said.
Sadr renewed a cease-fire last month, but issued a statement over the weekend authorizing his followers to defend themselves if attacked.
North of the capital, a gunfight Tuesday between police and unknown assailants killed at least nine people in Mosul, the city that U.S. commanders describe as the last urban stronghold of Sunni insurgents loyal to Al Qaeda in Iraq.
In Duluiya, also north of Baghdad, a suicide bomber in an explosives-laden minibus attacked a checkpoint run by policemen and local tribesmen paid by the U.S. military. At least five Iraqis were killed and 13 injured, including two children, police said.
Times staff writer Saif Hameed in Baghdad and special correspondents in Baghdad, Hillah, Mosul and Najaf contributed to this report.