Grainy footage showing the aftermath of the attack appeared on Twitter
At least 80 people, many of them Shia pilgrims, have been killed in a truck bomb attack at a road stop in Iraq, a security official says.
The blast struck at a petrol station and restaurant near Hilla, some 100 km (60 miles) south of Baghdad.
Busloads of pilgrims had stopped there on their way home from commemorating Arbaeen in the holy city of Karbala. Many Iranians were among the dead.
The jihadist group, Islamic State said it carried out the attack.
The attack happened close to the village of Shomali, 80 km (50 miles) south-east of Karbala.
Some reports say the suicide vehicle was parked, and the force of the blast completely destroying the petrol station.
Provincial security, chief Falah al-Radi told the BBC that Iranians were among the dead and wounded, and he feared the toll would rise.
It is a familiar tactic of IS militants to strike in one place when under pressure in another, says the BBC Middle East correspondent Orla Guerin. Iraqi forces are currently pounding the IS-stronghold of Mosul in northern Iraq.
Millions of Shia pilgrims travelled to Karbala to mark Arbaeen, the end of the 40-day mourning period for the third Shia Imam, Hussein. This year it took place on Sunday.
Hussein, the grandson of the Prophet Muhammad, was killed in battle at Karbala in the 7th Century on a day that is known as Ashura. His martyrdom is considered a defining event in the Sunni-Shia schism.
The Sunni militants of IS regard Shia as apostates because of their veneration of the Prophet’s family and other beliefs and practices.
Shia pilgrims are a target at this time of year, our correspondent adds. Although around 25,000 security forces were deployed to Karbala for the festival, some had returned to the front lines.
Last week six IS militants were confronted by security forces while on their way to Karbala, official said. Five were shot dead but the sixth blew himself up, killing eight civilians.
Deadliest bombings in Iraq in 2016.