Rebel fighters converging on the city of Aleppo say they are gaining the upper hand against Syrian government forces.
Rebels are badly outgunned in the city, and for days have been clashing with pro-Assad forces backed by artillery and helicopter gunships.
Government forces have said they were slowly clearing rebels out of the city, but the rebels say they are the ones making progress.
The Free Syrian Army (FSA) claims to have overrun two police stations in Aleppo, and other rebels say a key checkpoint north of the city, Syria's commercial capital, has also been captured.
The rebels received another apparent boost yesterday morning when American network NBC reported that the FSA had obtained a small supply of surface-to-air-missiles (SAMs) capable of shooting down the regime's helicopter gunships.
It is not clear how the rebels obtained the weapons, but Qatar and Saudi Arabia have been pushing for opposition forces to be equipped with the powerful missiles.
The fight for Syria's second city has become the focus of the 16-month-old rebellion against President Bashar al-Assad.
Middle East correspondent Matt Brown, who is just outside Aleppo, says if the rebels lose the city, they may well lose the uprising. He says because of that, rebels are trying hard to up the ante.
Local Free Syrian Army commander Abdel Jabbar al Akidi says tides are turning in the rebels' favour.
"Within days, God willing, Aleppo will be liberated," he told the BBC. "We've already taken some areas, and once they're secured, we'll move on to the city centre until the whole of Aleppo is free."
But despite recent rebel victories, many experts say they expect the government's overwhelming firepower to eventually wear down rebels in the city.
As the fighting goes on, there is also growing concern from Western diplomats about the make-up of the opposition forces.
Intelligence agencies have reportedly identified a steady flow of foreign fighters joining the fight in Syria — including militants from Chechnya, Yemen, Afghanistan and Pakistan.