A suicide truck bomb claimed by Islamic State killed at least 70 people at a gas station south of Baghdad Thursday. Many of the victims were Iranian pilgrims who had taken part in a Shi'ite holiday in the Iraqi city of Karbala.
Authorities say buses full of people were parked at the time and that numerous vehicles were torched by the force of the blast in the city of Hilla. The pilgrims were headed back to Iran after visiting Karbala for the Arbaeen observance. Arbaeen marks the end of a 40-day mourning period for the killing of Imam Hussein, a grandson of the Prophet Muhammad, during the 7th century. Imam Hussein's followers believe he was buried in Karbala.
Reports also say Iraqi security forces were on high alert for the duration of the pilgrimage, seen as a potential target of Islamic State. The terror group considers Shi'ites to be apostates.
The attack comes as Iraqi forces battle to retake the key city of Mosul from IS militants. Since October 17, Mosul has been under siege by forces trying to remove the IS fighters, who have controlled the city and other large swaths of Iraq for more than two years. Hundreds of thousands of civilians are believed to be trapped in Mosul even as Iraqi forces have begun clearing neighborhoods in the city's east.
The United Nations refugee agency says at least 60,000 people have fled the fighting in Mosul, Iraq's second city, since the military offensive began last month and that around 40,000 have done so since the start of November.