The report by Airwars, a project aimed at tracking the international airstrikes targeting the extremists, said it believed 57 specific strikes killed civilians and caused 48 suspected "friendly fire" deaths. It said the strikes have killed more than 15,000 Islamic State militants.
While Airwars noted the difficulty of verifying information in territory held by the IS group, which has kidnapped and killed journalists and activists, other groups have reported similar casualties from the US-led airstrikes.
"In this context, the present coalition policy of downplaying or denying all claims of noncombatant fatalities makes little sense, and risks handing (the) Islamic State (group) and other forces a powerful propaganda tool."
The US launched airstrikes in Iraq on Aug. 8 and in Syria on Sept. 23 to target the Islamic State group. A coalition of countries later joined to help allied ground forces combat the extremists. To date, the coalition has launched more than 5,800 airstrikes in both countries.