Updated

U.S. military officials say American airstrikes in Syria on Saturday killed up to 150 Islamic State fighters in a command center in the Middle Euphrates River Valley.

The U.S.-led coalition fighting the Islamic State says the strikes were near As Shafah, which is north of Abu Kamal in eastern Syria. They targeted an IS headquarters and were assisted by Syrian Democratic Forces who watched the area before the attack.

The coalition says there was a heavy concentration of fighters at the site and they appeared to be preparing to move. The large number of fighters killed in the attack underscores U.S. assertions that the Islamic State group continues to be a threat in Syria and hasn't been defeated.

The coalition says only IS fighters were killed in the strikes.