Nearly 500 people, among them 85 civilians, have been killed in a week of fighting pitting Syrian opposition against the jihadists from Islamic State of Iraqthe Levant .
Opposition Observatory said "we have documented the killing of 482 people in the fighting -- 85 civilians, 240 members of the rebel brigades and 157 members of ISIL. Among the civilians and rebels killed were 42 hostages who were executed in Aleppo by ISIL".
Opposition militants also executed 47 ISIS members, mainly in Idlib province in northwestern Syria.
The Opposition Observatory called for "crimes being committed in Syria to be brought before an international court".
Jihadists fighting has raged for a week, mainly in Aleppo, Idlib and Raqa provinces.
On Friday, opposition militants continued to advance in much of Aleppo and Idlib, where ISIL's presence was relatively weak, while the jihadists had the upper hand in Raqa, which has been under their control for several months.
Several opposition militant groups opened a new front against ISIL last week, accusing the jihadists of seeking control and committing horrific abuses in opposition areas.