The suicide bomber who stepped inside the gold-domed shrine in southern Pakistan in February was wearing a vest packed with ball bearings, bolts and screws. When he hit the detonator, he killed more than 80 people.

To the world, they were Muslims.

But to the Islamic State, which quickly claimed credit for the attack, they were something else: Mushrikin, an Arabic word meaning polytheists.

Because the worshipers who died at the shrine of the Sufi philosopher Lal Shahbaz Qalandar had come bearing offerings of rose petals and had prayed at the tomb of the revered saint, hard-liners saw their faith as an affront to Islam, which holds that there is a single, indivisible God.

Since at least 2016, Islamic State militants have targeted Sufis, who practice a mystical form of Islam that includes the veneration of saints, often at their tombs. The extremist group has systematically razed the tombs of Sufi saints and dynamited their shrines. Just over a year ago, the Islamic State began carrying out mass executions of Sufi worshipers during prayer.