German prosecutors have indicted a woman belonging to the Islamic State group's 'morality police' in Iraq for letting a small girl die of thirst in scorching heat.

The suspect, a 27-year-old German identified only as Jennifer W. due to local privacy rules, was deported from Turkey to Germany in 2016. She was arrested in June and has been charged with murder and committing a war crime.

'After the girl fell ill and wet her mattress, the husband of the accused chained her up outside as punishment and let the child die of thirst in the scorching heat,' read the statement.

Destroyed buildings from clashes are seen in the Old City of Mosul, Iraq July 2017

'The accused allowed her husband to do so and did nothing to save the girl.'

Federal prosecutors said Jennifer W. patrolled parks in Fallujah and Mosul in 2015, ensuring women adhered to IS dress and behavior codes.

'Her task was to ensure that women comply with the behavioural and clothing regulations established by the terrorist organisation,' said the statement.

A member of Iraqi Federal police walks along destroyed buildings from clashes in the Old City of Mosul, Iraq

'For intimidation, the accused carried an assault rifle of the type Kalashnikov, a pistol and an explosives vest.'

Prosecutors said W. and her husband bought a 5-year-old girl as a slave. The husband then left the girl chained outdoors as punishment for wetting her mattress with W. allegedly doing nothing to prevent her dying.

After the child's death, W. visited the German embassy in Ankara where she applied for new identity papers.

Thereafter, W. was arrested by Turkish security and extradited weeks later to Germany.

Due to a lack of actionable evidence against W., she was allowed to return to her home Lower Saxony, a state in Germany.

'Since then her declared goal has been to return to the territory under IS rule,' said the prosecutors.

In June this year, W. again tried to travel to Syria before German police arrested her.

No date has been arranged for the beginning of her trial. If found guilty, she faces up to life in jail.