Iraqi officials say a pair of suicide bombers detonated their explosives belts at a checkpoint south of Baghdad, killing nine people, including four members of the security forces.
The police and hospital officials said the Sunday attack near the holy Shiite city of Najaf also wounded 22.
There was no immediate claim of responsibility for the attack, which bore the hallmarks of Islamic militants.
The officials all spoke on condition of anonymity because they were not authorized to speak to the media.
It came one day after two suicide bombers killed at least 28 people at a Baghdad market.
That attack was claimed by the Islamic State group.
Baghdad has seen near-daily attacks blamed on Islamic militants since 2003.