Syrian rebels said a "barbaric and savage attack" was underway in a rebel-held Aleppo district, but denied claims by government troops to have captured the area, AFP reported.

Earlier Syrian forces claimed to have captured the Salaheddin neighbourhood after storming it and "annihilating" most of the insurgents.

The offensive came as Amnesty International raised concerns about the plight of civilians in Syria's commercial capital and warned both sides they would be held accountable for attacks on residential areas.

Early in the afternoon, state news agency SANA said "our brave armed forces have taken full control of the district of Salaheddin" and "inflicted heavy losses on groups of armed terrorists, killing or wounding a large number of them."

Dozens of rebels were captured, including foreigners, and others surrendered, SANA said. It said troops seized a large number of arms.

State television said the "armed forces dealt violent blows to the mercenary terrorists" in Salaheddin, "annihilating most of the terrorists."