Weapons supplied by the United States and Saudi Arabia to opposition fighters often fell into the hands of ISIL, significantly enhancing the "quantity and quality" of the group's armaments, a new report alleges.
The number of weapons goes "far beyond those that would have been available through battle capture alone", according to the study by arms-monitoring group Conflict Armament Research (CAR) published on Thursday.
The Weapons of the Islamic State report was based on a three-year field investigation in Iraq and Syriainto the group's arms and their origins.
It analysed more than 40,000 items found on the battlefield including weapons, ammunition, and materials used to make improvised explosive devices. Some wereacquired by ISIL through shifting alliances within the Syrian opposition.