Iraq must do more to ensure that thousands of women and girls who survived sexual violence by Islamic State group jihadists receive care, protection and justice, the UN said on Tuesday.

In a fresh report, the UN Assistance Mission to Iraq (UNAMI) and the UN rights office also warned that the children born as a result of the sexual violence risked facing a lifetime of discrimination and abuse.

"The physical, mental and emotional injuries inflicted by (IS) are almost beyond comprehension," UN rights chief Zeid Ra'ad Al Hussein said in a statement.

"If victims are to rebuild their lives, and indeed those of their children, they need justice and they need redress," he insisted.

Tuesday's report pointed to the horrific abuse suffered by women and girls, especially from the Yazidi minority, in IS-controlled areas, including rape, abduction, slavery and cruel, inhumane and degrading treatment.

In 2014, IS jihadists massacred Yazidis in Sinjar, forcing tens of thousands of them to flee, and capturing thousands of girls and women as spoils of war to be used as sex slaves.

The women were sold and traded across the jihadists' self-proclaimed "caliphate" in Syria and Iraq. Around 3,000 are believed to remain in captivity.

The UN report stressed that Baghdad was responsible under domestic and international law to prosecute the perpetrators and help ensure reparations for the victims.

It decried "gaps" in Iraq's criminal justice system, "which largely fails to ensure the appropriate respect and protection of women and children who have been subjected to sexual and other forms of violence."

It also warned that women who were married to IS fighters, with or without their consent, risked "discrimination and forms of collective punishment" based on the suspicion they cooperated with the group. 

The report raised particular concerns over the situation of hundreds of children born to women in IS-controlled areas without birth certificates or with IS-issued documents not accepted by Baghdad.

"The government must ensure (these children) are protected from marginalisation and abuse," Zeid insisted.

He urged Baghdad to ensure that these children are "neither exposed to discrimination through references on their birth certificate that they were born out of wedlock or have a father linked to (IS), nor left unregistered and at risk of statelessness, exploitation and trafficking," he said.

Source: AFP