The attacks come amid a week-long spike in sectarian violence following clashes at a Sunni protest camp in the north of the country.
Two parked car bombs went off simultaneously Monday morning in the city of Amarah near a gathering of construction workers and a market, killing 12 civilians and wounding 25, according to police. Amarah is located 320 kilometers (200 miles) southeast of Baghdad.
Another police officer said a parked car bomb exploded near a restaurant in the city of Diwaniyah, killing seven civilians and wounding 15 others. The city is located 130 kilometers (80 miles) south of Baghdad.
Two medical officials confirmed the casualty figures. All officials spoke on condition of anonymity as they were not authorized to release information.
Sectarian violence has spiked since Tuesday, when security forces tried to make arrests at a Sunni Muslim protest camp in the northern city of Hawija. The move set off a clash that killed 23 people, including three soldiers.
The Hawija incident and a spate of follow-up battles between gunmen and security forces as well as other attacks, including Monday's, have left around 200 dead in the last week.
Bomb attacks are relatively rare in Iraq's relatively peaceful southern Shiite cities.
No one has claimed responsibility for Monday's attacks, but coordinated bombings in civilian areas are a favorite strategy used by al-Qaida in Iraq.
Take ABC13 with you!
Download our free apps for iPhone, iPad, Android and Blackberry devices