A suicide truck bomb killed about 100 people, most of them Iranian Shiite pilgrims, at a petrol station in the city of Hilla 100 km (62 miles) south of Baghdad on Thursday, police and medical sources said.
Daesh militants claimed responsibility the attack in an online statement.
The group is also fighting off a US-backed offensive on its stronghold Mosul, in northe Iraq, in which Iranian-trained Shiite militias are taking part.
The gas station has a restaurant in its premises that is popular with travelers. Five pilgrim buses were torched by the force of the blast from the explosives-laden truck, a police official said.
Daesh has intensified attacks over the past month in areas out of its control in efforts to weaken the offensive launched on Oct. 17 to retake Mosul, the last major city under Daesh control in Iraq.
Iran’s Foreign Ministry condemned the attack without giving a casualties toll. Tehran will continue to support Iraq’s “relentless fight against terrorism,” ministry spokesman Bahram Qasemi was quoted as saying by Tasnim news agency.