A suicide bomber attacked a security checkpoint on a strategic highway south of Iraq's capital on Sunday killing at least 47 people.
Dozens more were wounded in the blast near the city of Hilla, which is about 90km south of Baghdad.
The Islamic State group claimed responsibility for the suicide bombing in an online statement circulated by supporters.
Over the past week, a double bombing at a market in Baghdad's Sadr city killed more than 70 people. The following day a suicide attack at a funeral north of Baghdad killed about 30.