The announcement from the US Central Command (Centcom) -- yesterday which oversees US military operations in the Middle East -- followed an internal investigation into six US airstrikes between July 28, 2015 and April 29, 2016.
"In each of the cases released today, the assessment determined that although all precautions were taken and the strikes complied with laws of armed conflict, civilian casualties unfortunately did occur," said Centcom in a statement.
Critics of the US-led air strikes have accused the coalition of underestimating the number of resulting civilian deaths.
The London-based Syrian Observatory for Human Rights said at least 56 civilians, including 11 children, died as they fled from a village near Manbij, a strategic waypoint between Turkey and the jihadist stronghold of Raqa.
According to the Observatory, around 600 Syrians, including 136 children, have been killed in coalition air strikes since September 2014.
Airwars, another London NGO, estimates that the international airstrikes in Syria and Iraq have killed more than 1,500 civilians.
Four more civilians died in Mosul on April 29 during strikes targeting the Australian Neil Prakash -- considered to be an influential IS group recruiter -- who also died in the bombardment.
In another strike on April 26 near Qayyarah in Iraq, one civilian died when a motorcycle "unexpectedly appeared in the target area after the US aircraft had already released its weapon," Centcom said.
"We deeply regret the unintentional loss of life and injuries resulting from our airstrikes and express our sympathies to those affected," Centcom said.