"ISIS's treatment of women and dealings with money were proving to be increasingly divisive within the organisation's own ranks," said a spokesperson for the Kurdistan Democratic Party (KDP).
Mosul in Iraq was seized by the ISIS in June last year.
The execution has reported just days after a UN official said she had witnessed the circulation of a child slave "price list" among ISIS fighters in Syria and Iraq, The Independent reported.
According to documents available, ISIS militants sell Yazidi and Christian women and children they have abducted. Girls aged just one to nine-years-old are sold at higher price.
ISIS captured hundreds of women of the Yazidi community after storming the Sinjar district in northern Iraq last year.
The sex slaves who somehow escaped ISIS's clutches have told of how they were forced to marry fighters who physically and sexually abused them.
An ISIS video released in November last year appeared to show an ISIS 'sex slave market' where fighters can choose among different Yazidi girls who are priced according to 'desirable' physical features.