The ICRC's Peter Maurer called for reconciliation in the country three months after the Iraqi government declared victory over the IS jihadists.

"This is a critical moment in Iraq and Iraqi politics," Maurer told a news conference in Baghdad after visiting the country's Sunni Muslim heartland of Anbar province.

The ICRC president cautioned against depriving the families of suspected jihadists of "regular access to brothers, fathers, husbands".

Many were worried about "where they are detained and by who, what is the future of their bread-giver," he told journalists.

Iraqi Prime Minister Haider al-Abadi in December declared victory over the Sunni extremist group after a years-long battle in which Shiite-dominated paramilitaries played a central role.

Pro-government forces detained some 20,000 suspected IS fighters, researchers say, but Iraqi authorities have not confirmed how many prisoners they are holding.

Maurer said some suspected jihadists' relatives had been confined to camps and were barred from moving freely.

Hundreds of women and children, both Iraqi and foreign, had been detained in Iraq, he added.

"The issue of foreign fighters is particularly complex," he said, adding the ICRC had been able to deliver assistance to some families in need.

Less than a month after world powers pledged $30 billion (24 billion euros) at a donors' conference on Iraq's reconstruction, Maurer said there were "still a lot of humanitarian needs".

Iraq remains the ICRC's second most important theatre of operations, he said, after war-ravaged Syria.