It said in a Thursday report that the al-Qaeda-linked Islamic State in Iraq and the Levant (ISIL), one of the most powerful terrorist groups to emerge from Syria's almost three-year-old conflict, is operating seven clandestine prisons in rebel-held areas.

Detainees are held for reasons ranging from suspected theft to offenses against the ideology of the ISIL such as smoking. Others are seized simply for challenging ISIL authority or belonging to rival armed groups, it said.

"Those abducted and detained by ISIL include children as young as eight who are held together with adults in the same cruel and inhuman conditions," said Philip Luther, Amnesty's Director for the Middle East and North Africa.

It described individuals being seized by masked men, held for weeks on end in solitary confinement at unknown locations and tried by self-styled courts that mete out death or floggings with little if any due process.

Former detainees described being beaten with rubber generator belts or cables, tortured with electric shocks and being forced into a painful stress position known as the "scorpion" in which the detainee's wrists are bound over one shoulder.

Amnesty said some people are detained for common crimes like theft while others are jailed for smoking or because they challenged ISIL's rule or belong to other armed groups.

In recent months, ISIL has kidnapped dozens of Syrian activists and news providers, as well as several foreign journalists.

BA/BA