Western support for military action against the Islamic State group is key to preventing attacks at home, French President Francois Hollande said Monday in Iraq, where yet another bombing killed dozens.

A suicide bomber detonated an explosives-laden car on a square in Baghdad's Sadr City neighbourhood, killing at least 32 people in the latest attack on the Iraqi capital claimed by IS.

Later the interior ministry said jihadist gunmen wearing suicide vests stormed a police station in the city of Samarra north of Baghdad, sparking clashes.

There were no immediate reports of casualties, but IS said it was also behind the Samarra attack.

France, one of the most active members of the US-led coalition fighting the Sunni extremist group, is particularly concerned over the return of a large contingent of French jihadists from Syria and Iraq.

"Taking action against terrorism here in Iraq is also preventing acts of terrorism on our own soil," he said at a base where French soldiers have been training elite Iraqi forces.

Hollande, the only major Western head of state to have visited Baghdad since the coalition was set up in 2014, stressed that supporting Iraq was one of the surest ways of securing Europe.

Of European countries targeted by attacks claimed or inspired by IS, France has been the worst hit, but there have also been attacks in Belgium and Germany.

Besides the defeated jihadists expected to return to Europe, radicalised children who grew up in the "caliphate" IS proclaimed in 2014 are also seen as ticking bombs.

"We will have to deal with the issue of the return of foreign fighters... who committed crimes, who brought their families with them, including in some cases very young children," Hollande said.

Since it joined the United States in the coalition in September 2014, France says its warplanes have conducted 5,700 sorties, around 1,000 strikes and destroyed more than 1,700 targets.

- 'Before summer' -

France has 14 Rafale warplanes taking part in coalition operations from Jordan and the United Arab Emirates.

It also has 500 soldiers training and advising elite Iraqi forces and CAESAR artillery vehicles stationed south of Mosul to support ongoing operations to retake the city.

Hollande met Iraqi President Fuad Masum, a Kurd, and Prime Minister Haider al-Abadi, from the largest Shiite political bloc, and called for reconciliation and unity after IS is defeated.

He then flew to the northern city of Arbil, capital of Iraq's autonomous Kurdish region, where he met local leader Massud Barzani.

He said just before leaving Iraq that he was told that the battle to retake Mosul, the last major jihadist stronghold in the country, could last several more months.

"It was confirmed to us that we could possibly achieve this goal in spring, in any case before summer," he said.

Hollande added that the focus would then move to Raqa, IS's other major bastion, in neighbouring Syria.

"If Daesh is eradicated in Iraq but remains in Syria, we know full well that acts will be carried out here in the Middle East but also on our own soil in France, in Europe," he said.

- IS bombings -

Hollande began his trip at a base near Baghdad where French forces are training Iraq's elite Counter-Terrorism Service, which has spearheaded most major anti-IS operations in Iraq since 2014.

It was CTS that first breached Mosul's city limits late last year in an effort to retake it from IS.

But the going has been tough for Iraqi forces, partly because hundreds of thousands of civilians have remained in the city, slowing their advance.

Abadi had promised his forces would rid Iraq of IS by the end of 2016, but last week said three more months would be needed to achieve that goal.

Some observers argue that the new timeline remains ambitious, given the continued IS presence in other parts of the country.

Hollande predicted Monday that 2017 would be "a year of victories against terrorism" but, while its "caliphate" appears doomed, IS still has the ability to sow chaos by attacking softer targets.

A suicide car bombing claimed by IS killed at least 32 people and wounded more than 60 Monday in Baghdad's Shiite-majority district of Sadr City.

Police said the bomber struck on a square where daily labourers were awaiting work, causing one of the highest casualty tolls in Baghdad in months.

The jihadists claimed another bombing on Saturday that killed at least 27 people in central Baghdad.

A US State Department statement branded the attacks "vicious acts of mass murder" and "a sobering reminder of the need to continue coalition operations" against IS.