Eleven of the 12 bombs struck in the evening, when streets are busier than usual during the Muslim holy month of Ramadan.
At least four people were killed and 42 others were wounded Thursday evening when a car bomb and three roadside bombs exploded in quick succession in Musayyiba, a town south of Baghdad, said an official with the Iraqi Interior Ministry.
The bombs went off near a Shiite shrine, and a number of Shiite pilgrims were among the dead and wounded, the official said.
Another roadside bomb near a Shiite shrine in Mahauil, south of Baghdad, wounded at least eight others, the official said.
At an outdoor market in Aun, near the Shiite city of Karbala, a sticky bomb affixed to a car killed two people and wounded three, the official said.
Two other bombings in Baghdad wounded five members of anti-al Qaeda groups known as Awakening Councils, the official said. A sticky bomb attached to the car of an Awakening Council member in southern Baghdad's Dora district wounded him and four of his guards, the official said.
Four of the eight people wounded in a bombing in a busy street in northern Baghdad's Kasra neighborhood were also members of the council, the official said.
Awakening Councils, or Sons of Iraq, are made up mainly of former Sunni insurgents who turned on al Qaeda in Iraq. They are credited for playing a key role in reducing violence across the country since 2007.
Earlier on Thursday, a car parked near a busy restaurant in Baquba blew up and wounded four people, local police said. Baquba is northeast of Baghdad in the provincial capital of Diyala.