Syrian and Russian warplanes pounded rebel-held east Aleppo on Sunday ahead of a UN Security Council meeting to discuss the worst surge in violence to hit the devastated city in years.
Overnight, residents and a monitor reported heavy air raids on the besieged east of the city, which Syria's army has pledged to retake.
The UN Security Council is due to meet later Sunday in an emergency session to discuss the escalating violence, which UN chief Ban Ki-moon described as "chilling".
Washington and its European allies meanwhile said the burden was on regime ally Moscow to save a truce that fell apart in the past week.
At least 101 people, mostly civilians, have been killed in Syrian and Russian bombardment of eastern Aleppo since the army announced an operation to take it Thursday, the Syrian Observatory for Human Rights said.
The monitor said at least 17 children were among those killed in the assault, which has included missile strikes, barrel bomb attacks and artillery fire.
On Saturday night, residents said cluster bombs rained down on eastern parts of the city, where an estimated 250,000 people are living under a government siege.
"All night long they were dropping cluster bombs. I couldn't sleep until four in the morning," said 62-year-old Ahmed Hajar, who was out looking for bread in Al-Kalasseh neighbourhood.
"Today the streets of my neighbourhood are full of unexploded cluster bombs. One person was killed when he disturbed one and it exploded," he added.
"It tore him apart... it was an awful scene."
- 'We're civilians here' -
In the nearby neighbourhood of Bab al-Nayrab, 30-year-old Imad Habush was baking bread in a small wood-burning oven outside his house.
"None of the bakeries are open anymore because of the bombing and the shortages of fuel and flour, so people have started making their own bread," he said.
"I don't know why the regime is bombing us in this barbaric way. We're civilians here, we're not carrying weapons, and we're besieged, we have no way to escape."
Once Syria's economic powerhouse, Aleppo has been ravaged by war and roughly divided since mid-2012 between government control in the west and rebel control in the east.
The eastern portion of the city has been under near-continuous siege since mid-July, prompting food and fuel shortages.
A truce deal hammered out by Russia and the United States this month was meant to see aid trucked into the east of the city.
But the ceasefire fell apart before any assistance was brought in, and the army and its Russian ally have since pounded the eastern neighbourhoods with a force that residents say is virtually unprecedented.
More than 300,000 people have been killed and over half the country displaced since the war began in March 2011 with anti-government protests.
Successive attempts to reach a political solution have failed, and the latest bid by Moscow and Washington has virtually collapsed, despite ongoing talks to save it.
- 'Chilling escalation' -
Ban said Saturday he was "appalled by the chilling military escalation" in Aleppo, and Britain, France and the United States requested an emergency meeting of the UN Security Council.
The meeting is scheduled for 1500 GMT, but it was unclear what results it could produce, with Moscow and Washington trading accusations over who is to blame for the ceasefire's failure.
The United States and its European allies said Saturday it was up to Moscow to save the truce.
"The burden is on Russia to prove it is willing and able to take extraordinary steps to salvage diplomatic efforts," read a joint statement from Britain, France, Germany, Italy, the United States and European Union.
"Patience with Russia's continued inability or unwillingness to adhere to its commitments is not unlimited," the statement added.
But Russia has blamed Washington for the ceasefire's failure, saying it did not uphold its commitment to ensure moderate rebels distanced themselves from jihadist groups like former Al-Qaeda affiliate Al-Nusra Front.
Syria's foreign minister meanwhile said Saturday that his government was confident of "victory" with support from "true friends" including Russia, Iran, and Lebanon's Shiite militant group Hezbollah.
"Our belief in victory is even greater now that the Syrian Arab army is making great strides in its war against terrorism," he told the UN General Assembly.
But on the ground, the army was pushed back from the strategic Handarat camp north of Aleppo city that they captured on Saturday, the Observatory said.
