Syrian state media say government forces have taken full control of a strategic district in the biggest city, Aleppo, after fierce fighting, according to BBC.
However, rebel commanders denied they had retreated from the Salah al-Din district, amid reports of a push by army tanks and armoured vehicles.
Images have emerged of dead bodies in shattered buildings, after the bombardment of a town near Aleppo.
The use of heavy weapons has been condemned by Amnesty International.
UK-based activist group the Syrian Observatory for Human Rights reports at least 20 deaths across Syria on Wednesday.
In another development, Jordanian officials confirmed that former Syrian Prime Minister Riad Hijab had only just crossed into Jordan - two days after his defection was announced.
Activists said he and his family had been hiding in the south of the country and that reports on Monday that he had already left Syria were aimed at throwing government forces off the trail.