The SDF's offensive,which began at the end of May,aims to remove Islamic State from areas it controls along the Turkish border.
The Manbij operation in which US special forces have played a significant role on the ground marks the most ambitious advance by a group allied to Washington in Syria since the United States launched its military campaign against Islamic State two years ago.
Manbij has been strategically important to the militants as a conduit for transit of foreign jihadists and provisions coming from the Turkish border.
Reuters pictures showed residents being released from an Islamic State-held neighbourhood on Friday and being welcomed by SDF forces.