A non-profit group estimates that at least 3,100 civilians have died in U.S. airstrikes in Iraq and Syria since August 2014, the start of the war against Daesh.
The U.S. military gives sharply lower estimates, saying such airstrikes have killed only 352 civilians, as reported by the New York Times.
But figures from Airwars, which tracks civilian deaths in Syira and Iraq, say that the civilian death toll is eight times higher than that what the U.S. has confirmed.
In addition, deaths in the first quarter of 2017 rose considerably, according to Airwars figures.
The New York Times wrote that operations to take Daesh strongholds such as Mosul and Raqqa played an important role in the higher death toll.
Another reason for the rising deaths could be changes in procedures for approving airstrikes, it reported.
The Times said that military commanders got more latitude in deciding on airstrikes in the final days of the Barack Obama administration, a trend which has grown this year under U.S. President Donald Trump.