Gunmen and suicide car bombers on Thursday killed at least 74 people, including Iranians, near the southern Iraqi city of Nasiriyah in an attack claimed by the militant Islamic State (IS) group.

The attackers struck at midday, opening fire on a restaurant before getting into a car and blowing themselves up at a nearby security checkpoint, officials said.

Abdel Hussein al-Jabri, deputy health chief for the mainly Shia province of Dhiqar, said at least 74 people had died, including seven Iranians, and another 93 people were wounded.

Security sources said the attackers were disguised as members of the Hashed al-Shaabi, a mainly Shia paramilitary alliance which has fought alongside the army and police against the IS in northern Iraq.

Jabri told AFP that many of the wounded were in serious condition.

The area targeted is used by Shia pilgrims and visitors from neighbouring Iran headed for the holy cities of Najaf and Karbala further north, although Dhiqar has previously been spared the worst of Iraq's violence.

The IS claimed responsibility for the attacks in a statement carried by its Amaq propaganda arm.

It said several suicide bombers had staged the assault on a restaurant and a security checkpoint, killing dozens.

The toll makes it the deadliest IS attack in Iraq since pro-government forces drove the militants out of second city Mosul in July.

The group regularly stages attacks in Iraq, where it has also lost swathes of territory to US-backed pro-government forces.

Thursday's attacks come as Iraqi forces backed by tribal fighters close in one of the last IS bastions in the country: the Al-Qaim area on the border with war-ravaged Syria.

The group's only other stronghold is Hawija, in Kirkuk province some 300 kilometres north of Baghdad.

IS has suffered a string of defeats on the battlefields of Iraq and Syria, leaving in tatters the cross-border “caliphate” it declared in 2014.

But any military offensive in Hawija is expected to be postponed due to a planned referendum on Kurdish independence.