"A report presented on Tuesday to the U.N. Human Rights Council said foreign Sunni jihadi militants and funds had poured into Syria where rebel factions including ISIL were wantonly abusing civilians in zones they controlled.
"A regional war in the Middle East draws ever closer. Events in neighbouring Iraq will have violent repercussions for Syria," the investigators' report said.
"Growing numbers of radical fighters are targeting not only Sunni (Muslim) communities under their control but also minority communities including the Shi'ites, Alawites, Christians, Armenians, Druze and Kurds," it said of Syria.
Its reference to Sunni militants targeting Sunni civilians involved forceful pressure on Sunni women to comply with sharia (Islamic religious law) and acts of revenge against Sunnis who had served in the Syrian government."