Syria's largest city had been bracing for a major showdown in anticipation of reports that dozens of tanks, as well as thousands of additional government forces, were en route to push back against a rebel offensive to seize the city of three million.
Mohammed Saeed, a local activist, told The Associated Press via Skype that clashes had been going on overnight, but that there were fears the worst was yet to come.
"Regime forces have been randomly shelling neighbourhoods and the civilians are terrified," Saeed told the news service.
"The government reinforcements have yet to arrive," he added.
According to activists, Syrian Army attack helicopters and fighter jets were deployed.
Last week, the combination of a heavy ground assault and artillery bombardments successfully quashed a rebel assault in the capital of Damascus. It appeared the troops were preparing for a similar tactic to retake Aleppo.
'Beginning of the end'
The stakes are high for both sides trying to wrest control of this battleground, freelance reporter Irris Makler told CBC News Thursday from Jerusalem.
"It's a vital city certainly for President Assad. It's Syria's largest city, it's Syria's wealthiest city, and so far it has been firmly behind him," she said, adding that the opposition claims to have control over half of Aleppo.
"If this city falls, it's a short march south towards Damascus. It is, in fact, the beginning of the end if this city falls. So Assad can't let it fall, and for that same reason, the rebels are there making this push."
In the mean time, casualties have been mounting in Aleppo. The Britain-based Syrian Observatory for Human Rights said that at least 26 people were killed in fighting on Tuesday, many of whom were children. Activists also said large numbers of people fled the southern neighbourhood of Sukkari on Wednesday.
While the government forces have managed to overpower the rebels, the fact it took a week to control the Damascus assault has been viewed as a sign that the opposition is growing stronger.
The rebels have been taking the fighting to areas that favour them, Makler told CBC News.
Canada willing to boost humanitarian aid
"What that means is they are in tiny areas, small alleyways the tanks can't get into," she said. "So we've seen footage over the past couple days that the rebels have released, of them running down these narrow alleys and tanks on fire, because they're using rocket-propelled grenade launchers."
As the uprising against President Bashar al-Assad reaches a climax, Canada's foreign affairs minister said talks were underway with Canada's allies over what to do about Syria's chemical and biological weapons, should the regime fall.
Chief among Canada's concerns is that the weapons could be used against the Syrian people, or that they could end up in the wrong hands — particularly those of Islamist extremists or al-Qaeda militants, who Middle East analysts believe may have infiltrated the rebellion.
For now, Baird said Canada will consider increasing its humanitarian aid commitment to help Syrians caught in the violence as the situation deteriorates, rather than to outright support military action in Syria.
Canada's current aid commitment of $8.5 million is the third-largest contribution by any donor country.
UNICEF launches emergency appeal
UNICEF on Wednesday launched an emergency appeal in Canada to support its Syrian emergency efforts.
The United Nations children's agency has said it needs $39 million from donor countries to support its humanitarian efforts in the region, where an estimated 1.5 million Syrians need help. So far, it says it's still $23 million short.
Meg French, UNICEF Canada’s director of international programs, told CBC News that their organization, one of the few on the ground, has been providing support for children and their families who have been displaced by the fighting.
French said many of the children are staying in schools and mosques, and being given food supplies and hygiene kits.
"Usually they have left quickly so they needed things to sustain themselves," she said, adding they have been able to reach about 190,000 people.
French said her organization is also providing psychological assistance to children.