The displaced had mostly left areas near Manbij that were held by ISIS in the last week, Farouk al-Mashi said, adding that their needs included food and medical aid.
"We urge the international community to take a humanitarian stand," he told Reuters by phone from Manbij.
Northern Syria has been a focal point of the Syrian war in recent weeks with most of the parties to the multi-sided conflict involved in one way or another.
Before the conflict, Manbij and its surrounding areas had a population of around 600,000.
The Russian-backed Syrian army has made a rapid advance against ISIS to the south of the city, while the Turkish military and Syrian rebel groups it backs have been fighting Manbij-based militia to the west of the city.
Manbij was captured from ISIS last year by an alliance of US-backed terrorist including the Kurdish YPG, which Ankara views as a threat to its national security because of its links to the Kurdistan Workers' Party (PKK).
The YPG and local militia forces in Manbij say the YPG subsequently left the city, though Turkey says that is not true.
The United States has deployed a small number of its forces in and around Manbij to ensure that the different parties in the area do not attack each other. The Manbij Military Council says the move followed Turkish threats to attack the city.