Iranian Foreign Minister Ali Akbar Salehi welcomed the cease-fire as a ‘‘positive action’’ in a telephone conversation with his Syrian counterpart, Walid al-Moallem, the semiofficial Fars news agency reported.

In Aleppo, it remained unclear how significant the rebels’ gains were, as their forces often push into new areas only to swiftly abandon them when the regime bombs their positions.

An Aleppo activist reached via Skype said rebel fighters had seized the predominately Kurdish neighborhood of Ashrafiyeh and were pushing into Al-Siryan al-Jadideh, a nearby Christian neighborhood, where they were trying to capture a security office used as an army post.

The advance expanded the fight for Aleppo from the poorer, mostly Sunni Muslim neighborhoods on its eastern and southern sides — where the rebels can often count on support from the local population — into a new section of the city farther north.

The city’s northwest has seen very little rebel activity since fighting in Aleppo began, and it was unclear how residents would react to the rebels, who are mostly from the countryside.

While the uprising has split Syria’s Kurds between the rebels and the regime, the country’s Christians have tried to remain neutral.

Abu Raed, the activist, said neither group had actively joined the uprising and that many were fleeing as the regime struck back.

‘‘They have started leaving the neighborhoods because the shelling has started,’’ he said.

Amateur video posted online Thursday showed gray smoke rising from a cluster of apartment buildings in Aleppo. A narrator said the video showed the aftermath of government shelling in the Midan neighborhood. In another video, a rebel fighter fired a machine gun from the back of a pickup truck before the vehicle sped off to take him out of the line of fire.

The videos appeared to be genuine, matching activist descriptions of events.

The Britain-based Syrian Observatory for Human Rights, which relies on a network of activists, said more than two dozen people were killed in the city Thursday, including eight Kurds who died when mortar rounds exploded in their neighborhood. It was unclear who fired them, it said.

The Observatory also said about 20 people were killed in shelling and clashes near Damascus, most of them in the restive suburb of Duma.

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