Since January, HRW said Iraq's judiciary had "proceeded with rushed trials against foreigners on charges of illegal entry and membership in or assistance" to IS.

It said most foreign women had been sentenced to death or life in prison and children aged nine and above to between five and 15 years in jail for taking part in violent acts.

The New York-based watchdog called on Iraq to change its approach.

"Iraq's 'one size fits all' approach to women who travelled to live under ISIS or to children whose parents brought them along is producing unjust outcomes in many instances," HRW's terrorism and counter-terrorism director Nadim Houry said in a statement.

"Iraqi justice should take into account their individual circumstances and actions and give priority to prosecuting the most serious crimes while exploring alternatives for lesser ones."

More than 300 people -- including some 100 foreign women -- have been sentenced to death in Iraq, and as many to life terms, for joining IS, judicial sources say.

Most of the convicted women are Turkish or from former Soviet republics.

In its statement, Human Rights Watch said sentences "should be proportionate to the crimes committed".

It said the "broad prosecution under terrorism charges of all those affiliated with ISIS... could lead to unfair results and ultimately dilute responsibility for the horrible crimes committed by ISIS."

HRW called on Iraq's judiciary to pursue the most serious crimes while exploring alternatives for lesser ones.

It said children should only be incarcerated as a last resort, and that the alternatives included "rehabilitative measures" with the aim of reintegrating them into society.