BAGHDAD — As workers gathered for breakfast on Thursday at a restaurant in Hilla, a Shiite-dominated city south of the capital, an explosives-laden car parked outside blew up, sending shrapnel ripping through the crowd. As an ambulance raced to the scene, another car was in pursuit, driven by a suicide bomber — who detonated his payload just as the first responders gathered.

The bombings in Hilla, in which security and hospital officials said 32 people were killed and 138 were wounded, were the worst in a day of insurgent attacks across Iraq. Other attacks in Karbala, a Shiite holy city in the south, Falluja, Mosul and Baghdad left 16 people dead and about 70 wounded.