US Coalition Airstrikes Kill 56 Civilians in Syria: Report

Among the casualties were 11 children, according to the report.

Among the casualties were 11 children, according to the human rights group.

Brett McGurk, the special presidential envoy for the Global Coalition to Counter ISIL, told reporters that he was unable to confirm reports and cautioned that the "initial allegations arose from ISIL’s official news channel."

He said the military takes extra measures to "make sure that every airstrike is really carefully vetted."

ABC News was unable to independently verify the figure.

"We take all measures during the targeting process to avoid or minimize civilian casualties or collateral damage and to comply with the principles of the Law of Armed Conflict," said Allen.

As of late May, the Observatory reports, at least 100 civilians have died from U.S.-led airstrikes targeting Manbij.