An annual pilgrimage to the holy Iraqi city of Kerbala comes to a violent end after an Islamic State suicide truck bomb killed about 100 people, most of them Iranian Shi'ite pilgrims who had paused at a highway rest stop.
Sunni IS considers all Shi'ites apostates.
But the militants are also fighting Iran-backed forces in the broader U.S.-led coalition to oust IS from their Iraqi stronghold Mosul.
Tehran condemned the attack, saying it will continue to support what it said was Iraq's relentless fight against terrorism.