U.S.-led coalition airstrike misfire kills 18 friendly Syrian troops

April 13 (UPI) -- The U.S-international coalition fighting the Islamic State said an airstrike misfire killed 18 members of the Syrian Democratic Forces, the allied force on the ground.

The coalition -- named the Combined Joint Task Force: Operation Inherent Resolve -- said the incident occurred Tuesday when the SDF battled the Islamic State, also known as Daesh, ISIL and ISIS, south of the Syrian city of al-Tabqah.

"The strike was requested by the partnered forces, who had identified the target location as an ISIS fighting position. The target location was actually a forward Syrian Democratic Forces fighting position," the coalition said in a statement. "The coalition's deepest condolences go out to the members of the SDF and their families. The coalition is in close contact with our SDF partners who have expressed a strong desire to remain focused on the fight against ISIS despite this tragic incident."

The coalition said it is investigating the cause of the mistaken airstrike, adding that it would "implement appropriate safeguards to prevent similar incidents in the future."

The SDF is on the ground in Syria with the support of the U.S.-led coalition in a large-scale offensive to capture the city of Raqqa away from Islamic State control.