Reports emanating from Syria indicate that Syrian rebels are stockpiling more ammunition and medical supplies in preparation for a major battle in Aleppo.
The rebels, who have gained control of large parts of Aleppo, Syria's second city, have set up checkpoints and sniper positions.
Activists say columns of government troops and tanks are heading towards the city from other areas.
Aleppo is the country's commercial capital, and is key to the battle for control of Syria’s northern region.
Street battles have been reported throughout Aleppo for almost a week, as rebels strive to hold on to seized neighbourhoods.
Reports say thousands of people are leaving as fears grow that an intense battle is looming.
The rebels are said to be reinforcing their ranks with more fighters, medical supplies, and ammunition such as Kalashnikov rifles.
But restive neighbourhoods have been pounded by artillery, mortars and helicopter gunfire from government forces in recent days.
And troops and tanks were reported to be heading to Aleppo from the city of Hama, and from the border posts with Turkey in Idlib province.
Activists say it is unlikely that the rebels will be able to hold on to the territory that they have gained if faced with a full assault from regime forces.
"They lack the strategic support and weaponry," said Talal al-Mayhani, an activist with connections in the rebel movement in Aleppo.
He said the battle for Aleppo was likely to play out in a similar way to an earlier battle in the capital Damascus, when rebels took control of large parts of the city before being forced to withdraw in the face of a government offensive.
Adrien Jaulmes, from the French newspaper Le Figaro, was travelling with the rebels around Aleppo on Wednesday and said they appeared to control about half of the city at most.
He said the rebels expected to be outgunned by the army, and intended to use guerrilla tactics when government reinforcements arrived.
In Damascus, where government forces have largely repelled a sustained assault by rebels, state TV reported more clashes in the southern district of Qadam.
The report showed army troops firing intensively as they moved into heavily damaged streets.
The government says its forces are trying to dislodge the "remnants of mercenary terrorist groups".
More than 16,000 people have been killed in Syria since the start of anti-regime protests in March 2011.
Repeated diplomatic attempts to stop the violence have foundered, with the UN Security Council bitterly divided.
Thousands of refugees have already sought shelter in Turkey, Lebanon, Jordan and Iraq.
And conditions throughout the country have worsened as the fighting has spread and intensified in the two main cities in recent weeks.