The US forces left the base of Sabta near the village of Surrin, south of the city of Ayn al-Arab in the northeastern countryside of Aleppo after removing all equipment, Xinhua quoted activists as saying on Monday.
They said tens of trucks left the US-run base after fully evacuating it, adding that nothing has been left but empty buildings.
Meanwhile, a well-informed source confirmed to Xinhua the evacuation of the base, providing video footage showing the US trucks passing through a Syrian-controlled site where Syrian soldiers held a Syrian flag and waved it in the face of the departing trucks.
The source said it was a large US convoy, adding that the forces will leave to neighbouring Iraq.
The Syrian Observatory for Human Rights war monitor said the US is planning to create three military bases in northeastern Syria, mainly in the city of al-Qamishli, which is controlled by the Kurdish-led Syrian Democratic Forces.
It's worth noting that the US has withdrawn a considerable number of forces from northern Syria to Iraq, mainly pulling out from areas that have been returned to the Syrian army after deals between the Kurdish forces and the Syrian army.
The recent development and redeployment of forces come in light of the current Turkish offensive against the Kurdish groups that has been dragging on in northeastern Syria since October 9.
( With inputs from IANS )