At least 73 people, mostly Iranian Shia pilgrims, were killed on Thursday in a suicide truck bomb blast at a petrol station in Hilla, about 100 km south of Baghdad, reported Reuters. The Islamic State group has claimed responsibility for the attack.

The incident took place when the pilgrims, who were on their way back to Iran from the Arbaeen pilgrimage in the city of Karbala, had stopped for a while at the fuel bunk that has a restaurant on its premises. Five pilgrim buses were up in flames when the truck exploded.

Iran’s Foreign Ministry condemned the attack but did not confirm the toll. United States, too, released a statement, condemning the attack. “The United States remains steadfast in its partnership with the Iraqi people and government and this attack only serves to strengthen our resolve in defeating Islamic State group,” National Security Council spokesman Ned Price said.

Violence has escalated in Iraq ever since the the Iraqi forces started closing in on the city of Mosul, which the militant group has held since 2014. The city is the Islamic State group’s last major stronghold in the country, and the international fraternity has express confidence that overpowering them would deal a strong blow to their operations.