Clashes were also reported in the densely-populated, poor neighbourhood of al-Sakhour.
Until now, Aleppo had escaped any serious violence, but the Free Syrian Army is inside the city and Mr Assad’s troops are fighting back. Activists claim up to 7,000 people have left the city.
Video uploaded to a social media website showed heavy armoured vehicles moving through a street in Aleppo.
Elsewhere in Syria, hundreds of people were also forced to flee their homes in Homs and have apparently crossed into neighbouring Lebanon.
The UN’s secretary general, Ban Ki-moon, said he was deeply distressed at the situation and once again urged the international community to find a peaceful solution to the conflict.
Amid the continuing violence, there were reports that two more Syrian generals have crossed the border into Turkey.
Video footage of one of them, Brigadier General Adelnasser Ferzat, showed him speaking in fluent Russian – perhaps under duress – directly to the Russian government, calling on them to stop supporting Mr Assads’s regime.
“We ask you, both the authorities and the people, to stand up for our freedom and right cause, for our will,” he says in the video.
Another senior military defector has claimed Mr Assad’s forces are set to use chemical weapons to “perpetrate a sea of blood”.
General Mustafa Sheikh, who fled the army in January, said regime forces wanted to “burn the country”.
“The regime has started moving its chemical stockpile andÂ redistributing it to prepare for its use,” he said.
“They are moving it from warehouses to new locations. They want to burn the country. The regime cannotÂ fall without perpetrating a sea of blood.”
Syria has denied any plans to use chemical weapons.
The country’s 16-month conflict has been transformed sinceÂ Wednesday, when a bomb killed four members of Mr Assad’s narrowÂ circle of lieutenants.
Those killed included his powerfulÂ brother-in-law, defence minister and intelligence chief.
Western and Israeli officials, concerned that chemical stockpiles could fall into the hands of militants, said a weekÂ ago that Syria appeared to be shifting weapons from storageÂ sites.
However it was not clear whether the operation was a securityÂ precaution or a preparation for deployment.
General Sheikh said the coming days would see increasedÂ shelling of Sunni Muslim strongholds in Damascus and Aleppo.
“The coming phase will witness a phase of bloodshed that isÂ unprecedented and the regime will resort to non-conventionalÂ weapons. Every action will trigger a bigger reaction.”
Meanwhile, United Nations Security Council has voted unanimously to extend its monitoring mission in Syria – after some of the worst violence of the uprising.
More than 50 people were killed in Damascus on Friday as rebels intensified their guerrilla fight to topple Mr Assad’s regime.
It was the sixth consecutive day of fighting in districts across the capital.
The rebels ambushed troops and attacked police stations as thousands of civilians fled to Lebanon and Iraq to escape the conflict.
The 30-day mission is considered crucial to implementing international envoy Kofi Annan’s six-point peace plan, which has been flouted by President Bashar al Assad’s government.
Some 300 unarmed observers suspended their mission last month because of escalating violence.
Source: London’s Biggest Conversation