Story highlights The parked truck exploded near several buses carrying Shi'ite pilgrims, a local official says

Pilgrims were in Iraq to commemorate the death of Imam Hussein, grandson of the Prophet Mohammed

Irbil, Iraq (CNN) At least 80 people were killed Thursday when a truck bomb exploded at a gas station in Iraq, the U.S. State Department said.

Most of the victims were Iranian Shi'ite pilgrims, according to authorities in Iraq.

ISIS, a Sunni terror group, claimed responsibility for the attack in a statement posted online.

"The flames of battles in Mosul will reach them in Baghdad, Karbala and Najaf," the ISIS statement reads. It also said Iranians were among those killed.

The blast happened on a highway southeast of Baghdad between Babel and Al-Qadisiyyah, said Falah al Radhi, the head of the Babel security council.

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