The Observatory said the death toll in Aleppo is expected to rise since many wounded people are in critical condition and rescue workers are still digging through the rubble.
Announcing the new offensive on state television late on Thursday, the Syrian government warned Aleppo residents to "stay away" from "terrorist positions". "The timing of the ground operation will depend on the results of the strikes".
"In Aleppo, negotiations are being conducted by fire", he said.
Elsewhere in Syria on Friday, the city of Homs, once one of the most active anti-regime cities in the country, finally conceded defeat. The pumping station supplying rebel-held parts of Aleppo was damaged on Thursday and subsequent strikes had made repairs impossible, Mr Dwyer told the BBC.
A truce deal negotiated between Moscow and Washington brought a few days of respite in Aleppo earlier this month, but no humanitarian aid before its total collapse this week.
On Saturday morning, the streets were almost empty, with just a few residents out looking for bread.
The aid convoy was hit by an airstrike that USA officials have said was carried out by Russian planes backing President Bashar al-Assad's regime.
Airstrikes that were halted during the ceasefire resumed this week in eastern Aleppo, according to the AMC activist.
This comes as the two allies bombed a strategic camp on the northern edge of Aleppo after losing control of it overnight, both rebels and the Syrian army say. Five of the victims were in al-Sukkari and 15 others in Bustan al-Qasr and Kallasseh. He described the meeting as "intense".
Residents speak of onslaught as Syrian army jets launch more than 150 air strikes, killing at least 90 people.
The US military did not dispute the strike, but characterized it as "unintentional" and relayed its "regret" to Syria through Russian Federation.
On Thursday at the United Nations, the United States and Russian Federation failed to agree on how to revive the ceasefire during what U.N. Syria mediator Staffan de Mistura called a "long, painful, hard and disappointing" meeting.
Russia's United Nations ambassador, Vitaly Churkin, blamed Syrian rebels for sabotaging the cease-fire by shoring up their forces.
Syrian government forces gather in the largely deserted Palestinian refugee camp of Handarat after capturing it from rebels.
Syrian President Bashar al-Assad on Thursday said the USA is not interested in a ceasefire, but that his government is ready and willing to commit to one.
Government forces and rebels have so far blocked the United Nations from establishing regular aid access to besieged areas in Syria.
"We have exchanged ideas with the Russians and we plan to consult tomorrow with respect to those ideas", US Secretary of State John Kerry said.
While Bayoush indicated rebel capabilities could be enhanced to a degree, he said a more significant shift would be in their tactics, though he gave no details.
After the second planned ceasefire in Syria collapsed on Monday, the Syrian army is working to retake the parts of Aleppo that are now held by rebels. "Any truce, seven days, three days would be senseless", he said, adding that in any case the US -led coalition had proved its inability to control rebels.