IRBIL, Iraq — At least 80 people, many of them Shi’ite pilgrims on their way home to Iran, were killed Thursday when an Islamic State suicide bomber detonated a truck filled with explosives at a roadside service station in southern Iraq, local officials said.

The attack came two days after Prime Minister Haider al-Abadi applauded the security forces for protecting the millions of Shi’ites who have flowed through southern Iraq in recent days for what many consider the world’s largest religious pilgrimage, larger even than the hajj in Saudi Arabia.

In years past, the annual rite known as Arbaeen, a commemoration of the martyrdom of the revered seventh century Shi’ite figure, Imam Hussein, was a frequent target of Sunni extremist groups.

Up until the bombing Thursday, which the Islamic State claimed in a statement, the event had been mostly carried out safely. That was seen as a success for Abadi and the military, and it was hailed as a sign that the government could keep pushing a major offensive against the Islamic State in Mosul, while protecting pilgrims in the south.

The bombing, in Hillah, south of Baghdad, shattered that illusion. The Islamic State remains a potent force, both on the battlefields of Mosul, where fighters are putting up a last stand against Iraq’s elite forces in eastern neighborhoods, and in its ability to carry out traditional attacks.

That attack alarmed US officials, who worry that efforts to defeat the Islamic State in Mosul will be squandered if civilians around the country are terrorized by bombings.

New York Times