"In Syria, we are experiencing historic moments as we witness the fall of the authoritarian regime in Damascus", says commander Mazloum Abdi in a statement on Telegram.
He also writes that the regime's fall means "an opportunity to build a new Syria based on democracy and justice that guarantees all Syrians' rights."
At the same time, reports are emerging that Syrian rebels are attacking Kurdish militia in the city of Manbij in the northern part of the country, according to the news agency NTB, citing opposition sources.
Manbij is located about 90 kilometers northeast of Aleppo and has been controlled by Kurdish-led SDF in recent years.
The SDF alliance is dominated by the Kurdish YPG militia, which is the armed branch of PYD, the largest political party among Kurds in Syria. Turkey equates YPG and PYD with PKK.