The ultra-hardline Sunni Muslim group were driven out of Shirqat on Thursday by US-backed Iraqi forces. Last month it lost the Qayyara oilfield, south of Mosul, to government forces thrusting northwards in an offensive to retake the largest city under IS control.
Deprived of oil income, IS will have to find other financing means such as increasing taxation and fines in areas still under its control, said Muthana Jbara, a provincial security official.