There was no public transportation, and hospitals were appealing for blood donations, he said.

“We fear the government’s retaliation,” said Ahmad, a resident of the southeastern Salaheddiin neighborhood, where so many insurgents poured in from the countryside that they sometimes ended up fighting one another for control of individual streets, residents said.

People streamed out of the neighborhoods where the rebel soldiers claimed control, figuring they would be pounded by government forces, following the same pattern in one Syrian city after another during the course of the 17-month-old uprising. But some men stayed behind to protect their property from looters.

Residents in the outlying districts said refugees from the inner city had taken over schools and parks to live in. Many of them were fleeing for a second time, having come to Aleppo from central cities like Homs and Hama where the government began attacking months ago. In Aleppo, the neighborhoods where the rebels established toeholds were mostly poor and on the eastern side of the city.