Al Jazeera has gained rare access to areas in eastern Afghanistan held by ISIL.
The fighters say they are gaining territory from Afghanistan's largest armed group, the Taliban. And in areas under ISIL control, young children are being trained to become fighters and suicide bombers.
Al Jazeera's Osama Bin Javaid explains.
Watch the full documentary, ISIL and the Taliban, on Al Jazeera at 20:00 GMT on Sunday, November 1
Source: Al Jazeera