The explosion near a maternity hospital occurred as the streets were packed with shoppers and people on their way to work.
The explosion also set at least 10 cars ablaze.
Al-Hillah, about 100 kilometers south of Baghdad, has been the site of some of the country's deadliest bombings, including a double suicide attack in March that killed 120 people.
Searching For A Way Forward
LOOKING BEYOND AL-MALIKI: RFE/RL Iraq analyst Kathleen Ridolfo led an RFE/RL briefing about the changing political landscape in Iraq, focusing on efforts to gain the upper hand in the event that the government of Prime Minister Nuri al-Maliki falls.
LISTENListen to the entire briefing (about 70 minutes):
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Opposition Appears Set On Bringing Down Al-Maliki
Former Premier Pushing New Plan For Reconciliation
Al-Sadr Prepares For Post-Coalition Era
Sunni Ultimatum Rocks Al-Maliki's Position
THE COMPLETE STORY: RFE/RL's complete coverage of events in Iraq and that country's ongoing transition.