BEIRUT — A misdirected airstrike by the U.S.-led coalition earlier this week killed 18 allied fighters battling the Islamic State group in northern Syria, the U.S. military said Thursday.

U.S. Central Command said coalition aircraft were given the wrong coordinates by their partner forces, the predominantly-Kurdish Syrian Democratic Forces, for the strike on Tuesday that was intended to target IS militants south of their Tabqa stronghold, near the extremists’ de facto capital, Raqqa. The strike hit an SDF position instead.