The coalition had no immediate comment.
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 U.S.-led airstrikes.
