At least 73 people were killed in a suicide attack on a road between Iraq’s central cities of Hillah and al-Diwaniyah, the Iraqi police have said.
Another 105 people were injured when a suicide bomber driving a car with explosives targeted eight buses at a petrol station.
Most of the passengers in the buses were Shiite Iranian pilgrims coming from the city of Karbala.
The Islamic State extremist Sunni militia claimed responsibility for the attack using the Telegram messaging app.
Islamic State considers Shiites to be heretics.
On October 17, joint Iraqi forces, supported by US-led alliance air cover, began an offensive to dislodge Islamic State from its last stronghold in the city of Mosul.