The U.S. military says an internal investigation shows that 14 civilians were killed and one civilian was wounded in six separate U.S. airstrikes in Iraq and Syria between July 2015 and April 2016.

The conclusions were reported Thursday by U.S. Central Command, which oversees U.S. military operations in the greater Middle East. Central Command regularly investigates reports of civilian casualties from airstrikes when it finds or is alerted to what it considers credible evidence.

It said the deadliest of the six airstrikes was on April 29 in Mosul, Iraq. The attack targeting a Daesh leader killed four civilians.

Central Command said the strikes complied with laws of armed conflict and expressed regret for the unintentional loss of life and injury.