The panel said Syrians and Iraqis are subjected to an Islamic State "rule of terror" from its calculated use of public brutality and indoctrination to ensure the submission of communities under its control, and that the tactics include repeated violations against children and women.
The conclusions from the Independent International Commission of Inquiry on Syria, a four-member panel of independent experts, are based on more than 300 interviews with people who fled or are living in IS-controlled areas and on collected video and photographic evidence.
Commission member Vitit Muntarbhorn told reporters in Geneva the report is meant to amplify the voices of victims, who describe executions, amputations, public lashings and the use of sexual slavery, child soldiers and widespread indoctrination.
The group has "become synonymous with extreme violence directed against civilians and captured fighters," the report said.
"The group deploys its fighters and materiel in close proximity to civilian areas," the report concludes, adding that since US-led airstrikes began civilians living in the northern Syrian town of Manbij have described IS fighters positioning themselves in local homes and farms.
The 47-nation Human Rights Council in Geneva authorised the commission to investigate all alleged violations of international human rights law since March 2011 in Syria and to identify whenever possible those responsible, so that they can be prosecuted.
