A barrel bomb killed a family of six in rebel-held eastern Aleppo early on Sunday and rebel shelling took the lives of eight children at a school in the west, as one of the heaviest government bombardments of Syria's civil war continues.
Two medics said the al-Baytounji family suffocated to death because the barrel bomb, which fell in the Sakhour district at about midnight, had been laced with chlorine gas.
The UK-based Syrian Observatory for Human Rights, which monitors the war through a network of informants, confirmed the bombing but could not confirm that chlorine gas was used.
Damascus has denied use of the gas, which would contravene the international Chemical Weapons Convention.
Rebel shelling killed at least eight children, aged six to 12 years, among 10 deaths in the Saria Hasoun school in al-Furqan district, the Syrian Observatory and Syrian state television reported.
Hundreds of people have been killed since Tuesday as the government and its allies attempt to quash resistance in Aleppo's rebel-held eastern zone.
The UN's Syria envoy Staffan de Mistura warned on Sunday that time was "running out" for eastern Aleppo as he expressed international outrage over the bombing campaign.
Syria's military and Russia's air force had paused their bombardment of eastern Aleppo, except for on the frontlines, for two weeks after a month-long offensive from late September to late October, but recommenced air strikes on Tuesday.
The plight of civilians in eastern Aleppo was underscored on Saturday when the World Health Organization reported that the bombing had put all the hospitals in the besieged district out of operation. An official with a rebel group based in east Aleppo said there were still no working hospitals there on Sunday.
The army and its allies began ground attacks on Friday and the Observatory reported intense clashes in Sheikh Saeed in southeast Aleppo and in Baeedain and Bustan al-Basha in northeast Aleppo.
Top UN officials said on Saturday that they were "appalled" by escalating violence in Syria, and urged immediate access to Aleppo, where government forces are waging a ferocious assault to retake rebel-held districts.
"The United Nations is extremely saddened and appalled by the recent escalation in fighting in several parts of Syria and calls on all parties to cease indiscriminate attacks on civilians and civilian infrastructure," the UN's humanitarian coordinator for Syria Ali al-Zaatari and regional humanitarian coordinator Kevin Kennedy said.
'All of Syria' at stake
An inquiry by the UN and the Organisation for the Prohibition of Chemical Weapons has said that Syrian government forces have used chlorine gas in barrel bombs at least three times during the war. Damascus denies it.
Syria also denies using barrel bombs - improvised ordnance made of oil drums filled with high explosive and shrapnel and dropped from helicopters. Their use has been condemned by the UN for causing unnecessary suffering.
Air strikes continued to hit several districts of eastern Aleppo on Sunday, the Syrian Observatory said, after at least 54 people were killed in bombing on Saturday.
So far about 240 people have been killed in bombing in east Aleppo and the rebel-held countryside to the west of the city since Tuesday, it added.
The French foreign minister on Sunday condemned Syrian government air raids.
Jean-Marc Ayrault's comments to Al Jazeera came after he met representatives of the opposition Syrian High Negotiations Committee in Qatar's capital, Doha.
"Today's war is all-out war. I condemn this in the name of France. I will take the initiative to bring together those who share the same vision for Syria’s future in the coming hours and days," he said.
"You can't stand there and wait for Aleppo to fall. Because it is not only Aleppo at stake - it is all of Syria."
'Chlorine gas' attacks
Syria's Foreign Minister Walid al-Moallem said in a televised news conference that de Mistura discussed the possibility of an autonomous administration being set up in eastern Aleppo, but that Damascus completely rejected this. An elected city council oversees services in the rebel-held eastern districts.
Moallem said that the arrangement was intended by rebel groups to control distribution of food, and they were holding the civilians of eastern Aleppo hostage.
Asked about Damascus' expectations from US President-elect Donald Trump, Moalem said he wanted him to stop arming rebel groups and to curb regional powers who did so.
Video of the Syrian family killed was distributed online by the medics. It showed the bodies of four children stretched out on a floor, their lips blue and dark marks around their open eyes.
Medics and residents in rebel-held areas often accuse the Syrian military of using chlorine in barrel bomb attacks, but the difficulty in reaching besieged areas makes it hard for international agencies to verify the claims.
Syria and Russia have also accused the rebels of using toxic gas in artillery shells, including during a major assault on the western fringe of the government-held zone in Aleppo early this month.