The Shi’ite holiday of Arbaeen is continuing to be used as a target for ISIS attacks, with the latest attack today in the city of Hilla, south of Baghdad, seeing an ISIS truck bomb doing after a large group of Iranian Shi’ite pilgrims.

The pilgrims were stopped at a gas station and adjoining restaurant when the truck bomb was detonated, and around 100 civilians, overwhelmingly the pilgrims, were reported slain in the attack. Five pilgrim buses were destroyed in the strike.

The pilgrims were returning to Iran after Arbaeen, during which they had visited the important Shi’ite religious city of Karbala. Arbaeeen is held 40 days after the bigger holiday of Ashura, both of which attract huge numbers of pilgrims. With growing sectarian tensions in the Middle East, some Shi’ite pilgrims are choosing to go to Karbala as an alternative to a Hajj to Mecca.

Since the 2003 US invasion of Iraq, the Shi’ite pilgrimages have attracted large numbers of attacks by Islamist groups like ISIS, and its predecessor faction. This means multiple attacks annually during these holidays, though it does not appear to greatly deter the pilgrims.