A bomb apparently targeting buses of Shiite Muslim pilgrims heading home from a religious celebration in Iraq claimed dozens of lives Thursday.

Initial reports indicated at least 80 people were killed and "many more" were injured, the White House said in a statement about the suicide truck bombing near the city of Hilla. The Islamic State, also known as ISIL or ISIS, claimed responsibility for the assault in a statement on its Aamaq news agency.

"These murders are yet another example of Daesh's contempt for human life and its efforts to sow discord and division among the Iraqi people," State Department spokesman John Kirby said in a statement. "Our partnership with Iraq and its people, who serve on the front lines of this global fight, remains steadfast and unwavering."

The blast occurred about 75 miles southeast of the capital of Baghdad, where buses carrying pilgrims returning from the city of Karbala were parked, AFP reported. They had traveled to Karbala, about 50 miles from the attack scene, for the annual Arbaeen pilgrimage to the Hussein mosque.

The target of the attack appears to have been a bus carrying Iranian pilgrims, officials told the Associated Press on condition of anonymity because they were not authorized to speak to the media.

There were at least seven buses containing pilgrims from Iran, Bahrain and Iraq at the gas station, AFP reported. At least 20 Iranians were among the dead, according to the AP.

There has been an uptick in suicide and car bombings since Iraqi security forces launched an operation to drive ISIL extremists from Mosul, Iraq's second-largest city.

On Thursday, Iraqi troops drove ISIL militants from three more neighborhoods in Mosul. Brig. Gen. Haider Fadhil of the special forces told the Associated Press his men have retaken the neighborhoods of Amn, Qahira and Green Apartments and were expanding their foothold in the densely populated district of Zohour.

Contributing: Associated Press