A U.S.-backed alliance of Syrian Kurds and Arab rebel groups, supported by U.S. coalition planes, captured a dam on Saturday from the Islamic State group, cutting one of its main supply routes across the Euphrates, an alliance spokesman said.

Col. Talal Selo said the seizure of the Tishrin dam helps isolate the militants' strongholds in northern Aleppo from their territories east of the Euphrates River, where Raqqa, their de facto capital, is located.

Selo said the rapid advance overnight by thousands of troops from the Democratic Forces of Syria had brought the dam upstream from Raqqa under their control on Saturday afternoon.