UN says ISIS leaders liable for war crimes

Islamic State commanders are liable for war crimes on a "massive scale" in northeast Syria, calling on world powers to bring the IS commanders before the International Criminal Court, United Nations (UN) investigators said.

Their report, based on over 300 interviews with witnesses and victims, called on world powers to bring the commanders to face justice for both war crimes and crimes against humanity, including beheading, stoning, and shooting civilians and captured fighters.

"In carrying out mass killings of captured fighters and civilians following military assaults, ISIS (Islamic State) members have perpetrated egregious violations of binding international humanitarian law and the war crime of murder on a massive scale," said the report.

Foreign fighters have dominated the group's ranks and dominate its leadership structure, the report said. A separate U.N. report has said 15,000 foreigners have gone to fight in Syria and Iraq.

"The commanders of ISIS have acted wilfully, perpetrating these war crimes ... They are individually criminally responsible," the report added, saying the group's leader, Abu Bakr al-Baghdadi, wielded "absolute power".

The report found that ISIS was depriving 600,000 people in the north of deliveries of food and medical aid, and enforcing its radical interpretation of Islamic law through "morality police".

These ordered lashings and amputations for offences such as smoking cigarettes or theft; one female dentist in Deir al-Zor had been beheaded for treating patients of both sexes.

Children were being pressed to inform on their parents, women stoned for unapproved contact with men, and Christians, Kurds and other minorities forced to convert to Islam or pay a tax: "Witnesses saw scenes of still-bleeding bodies hanging from crosses, and of heads placed on spikes along park railings."