An air strike carried out by the U.S.-led coalition fighting the Islamic State (IS) extremist group has mistakenly killed 18 allied fighters in northern Syria, the Pentagon says.
An April 13 Pentagon news release said coalition aircraft were given the wrong coordinates by "partnered forces" for a strike intended to target IS militants south of the town of Tabqa.
It said the April 11 strike hit a forward position of the predominantly-Kurdish Syrian Democratic Forces (SDF) instead, killing 18 fighters.
The Pentagon expressed the coalition's "deepest condolences" to SDF members and their families.
SDF troops backed by air and ground support from the U.S.-led coalition have surrounded Tabqa, which is located on the Euphrates River next to a dam and military airport and near the IS stronghold of Raqqa.