The regime has been bombarding the rebel-held areas using TNT-packed barrels since December 15, in an offensive the Syrian Observatory for Human Rights said has left 410 people dead, including 117 children, as of Tuesday night.
Also among those killed were 34 women, 30 rebel fighters and nine jihadists.
The Britain-based Observatory, which uses a network of contacts inside Syria to track the conflict, said the air force pressed the assault into an 11th day on Wednesday.
It said later that mortar fire killed six people and wounded 15 in regime-controlled neighbourhoods of Aleppo, including Midan and Sulamaniyeh.
Human Rights Watch has labelled as "unlawful" the relentless aerial campaign by President Bashar al-Assad's regime, especially the use of the massively destructive barrel bombs in civilian areas.
The United States has also condemned the assault, and on Wednesday the Arab League and the European Union joined the chorus of criticism.
"The High Representative (Catherine Ashton) is deeply concerned with reports of an escalating bombing campaign," said the EU. "She condemns the unabated use of air strikes by the Syrian government on civilian areas."
Arab League chief Nabil al-Arabi called on "the Syrian army to stop the air bombings" of Aleppo, condemning the killing of "hundreds of innocent civilians".
Arabi also called on the UN Security Council "to take responsibility" to end the conflict.
The opposition National Coalition has said it will boycott a peace conference slated for January if the Aleppo bombing does not cease.
A security source in Damascus has defended the campaign as necessary to "save Aleppo".
"We do not target any area unless we are 100 percent sure that the ones there are terrorists," the source said, using the regime term for rebels.
"The bodies you see on television are the bodies of terrorists and mercenaries, most of whom travelled into Syria from abroad."
Syria hit back at the US on Tuesday, describing it as a "one-eyed pirate" for condemning the assault but "ignoring the crimes committed by the terrorists".
'Too many lives shattered'
In his first Christmas address, Pope Francis urged peace in Syria, saying "too many lives have been shattered... fuelling hatred and vengeance".
"Let us continue to ask the Lord to spare the beloved Syrian people further suffering, and to enable the parties in conflict to put an end to all violence and guarantee access to humanitarian aid."
In a landmark deal Wednesday, the Syrian government and rebel forces in a besieged town near Damascus agreed on a truce to allow much-needed aid supplies to residents trapped in the Moadamiyet al-Sham area.
"A truce came into force on Wednesday, and the people have accepted as a gesture of goodwill to fly the regime flag over the town's water towers," said Abu Malek of the town's opposition council.
Abu Malek said if the truce went well, rebels would hand over heavy weapons but regime forces would stay out of the town.
A source close to the regime confirmed the truce, but said the army would enter the town to ensure all weapons had been handed over.
The conflict is estimated to have killed more than 126,000 people since it started in March 2011.
But in a new sign of confidence, Syria's Oil Minister Suleiman Abbas and General Petroleum Company signed a major oil and gas exploration deal with Russia's Soyuzneftegaz energy firm.
The 25-year deal "is the first ever for oil and gas exploration in Syria's waters," head of the General Petroleum Company Ali Abbas told AFP, adding it would be financed by the Russian side.
Moscow is one of Assad's main backers, as well as a key proponent along with the United States of peace talks slated for January 22 in Switzerland.