Many of the civilians who fled used side roads to reach government-held areas because the main highway was blocked with barriers at a checkpoint that previously was controlled by the Kurdish-led and U.S.-backed Syrian Democratic Forces, Associated Press journalists observed.

In the space of two days, the Syrian military, aided by tribal militia, has driven Kurdish forces from wide swathes of northern Syria that they have held for more than a decade.

The Syrian army continued its push into Kurdish-held territory on Saturday, despite U.S. calls to halt its advance in towns in the area in Syria's north.

The Syrian military claimed Tuesday that guards from the Kurdish-led Syrian Democratic Forces had abandoned a camp in northeast Syria housing thousands of people linked to the Islamic State group, allowing the detainees to escape.