The United States military announced Thursday that a misdirected airstrike in northern Syria killed 18 Syrian fighters allied with the U.S.
The strike occurred on Tuesday, according to U.S. Central Command.
Centcom reported that the aircraft received the wrong coordinates from the Syrian Democratic Forces, a predominantly Kurdish allied group. The strike was intended to hit Islamic State-aligned militants to the south of Tabqa, an ISIS stronghold. The SDF, supported by air and ground support from the U.S.-led coalition, have surrounded Tabqa.
Due to the improper coordinates, the strike instead hit an SDF site, killing 18. It remains unclear which coalition member's air force is responsible for the strike.
The announcement followed the U.S. intelligence community's interception of communications between Syrian military and chemical experts. A senior U.S. official told CNN that the communications involved discussions of preparations for last week's chemical weapons attack. The intercept was part of a broader review of all intelligence to establish responsibility for the attack.
U.S. officials have said there is "no doubt" that the attacks are the doing of Syrian President Bashar al-Assad.
The Trump administration responded to the gas attack with a missile strike last Thursday. According to Secretary of Defense James Mattis, the strike destroyed "fuel and ammunition sites, air defense capabilities, and 20 percent of Syria's operational aircraft."
Note: This article has been updated with more information.