Police said it appeared whoever set the bombs in a parking garage waited until the first two had gone off and crowds gathered before setting off the third, a BBC correspondent reported.

The city council's security chief told the broadcaster the majority of casualties came from the third blast.

The city is in the largely Shiite southeastern province of Maysan, where various militias are vying for power, CNN said.

British coalition forces had been responsible for security in the province since the U.S.-led invasion in 2003, but turned control over to Iraq's own forces in April.