A barrel bomb killed a family of six in opposition-held eastern Aleppo early today, a war monitor, a member of the opposition and two medics said, while state television claimed that rebel shelling killed seven children at a school in the government-held western sector.

Syrian medics said the Al-Baytounji family had suffocated to death because the barrel bomb, which fell in the Sakhour district at about midnight, had been laced with chlorine gas.

Media loyal to the Assad regime claimed that rebel shelling killed at least seven children among ten deaths in the Saria Hasoun school in the Al-Furqan district.

The Syrian regime of President Bashar Al-Assad has been known to use chemical weapons against civilian targets in almost every major city in Syria since the war began in 2011.

Hundreds of people have been killed since Tuesday in one of the heaviest bombardments of the country’s civil war, now in its sixth year, as the government and its allies attempt to quash resistance in Aleppo’s opposition-held eastern zone.

Syria’s military and Russia’s air force claimed to have observed a unilateral pause in the bombardment of eastern Aleppo, except for on the frontlines, after a month-long offensive from late September to late October, but recommenced strikes on Tuesday.

Observers commented that the unilateral ceasefire was not honoured, and that the definition of “frontlines” used by Russia and Syria was very vague, allowing a near constant barrage against densely populated regions throughout the country.

An inquiry by the United Nations and the Organisation for the Prohibition of Chemical Weapons (OPCW) has found that Syrian government forces have used chlorine gas in barrel bombs at least three times during the war.

Syria also denies using barrel bombs – improvised ordnance made by oil drums filled with high explosive and shrapnel and dropped from helicopters – despite hundreds of video clips providing ample evidence that they are.

Their use has been condemned by the United Nations for causing unnecessary suffering.

Staffan De Mistura, the envoy of the United Nations secretary general, arrived in Damascus for talks with Syrian Foreign Ministry officials today with Aleppo on the agenda.

However, Syrian Foreign Minister Walid Al-Muallem rejected De Mistura’s offer for eastern Aleppo to have an autonomous administration as a temporary measure to end hostilities, Syrian state broadcasters revealed not long after the meetings with the UN official.

Airstrikes continued to hit several districts of eastern Aleppo early today, the Syrian Observatory for Human Rights (SOHR), a UK-based war monitor said, after at least 54 people were killed in a sustained bombing campaign by the Russia-backed Syrian air force yesterday.

The two medics identified the family in a film distributed online. It showed the corpses of its four children stretched out on a floor, their lips blue and dark marks around their open, lifeless eyes.

One of the medics, Abu Al-Abbas, has a colleague who lives on the same street. Another was the manager of a hospital and said doctors had confirmed the cause of their death as gas poisoning. A rebel official, Zakaria Al-Malahifji, from the Fastaqim group, also said they had been killed by gas.

The civil war pits the Assad regime backed by Russia, Iran and Shia militias from Iraq, Lebanon and Afghanistan against mostly Sunni opposition factions, including groups supported by the United States, Turkey and Gulf monarchies.

Aleppo has become the focal point for fighting, as the army and its allies attempt to end resistance there, alternating intense bombardment and ground attacks with offers to the opposition to quit the city during periods of reduced bombing.

The use of siege and bombardment tactics has previously forced opposition fighters to surrender other encircled areas such as the large town of Daraya southeast of Damascus, seen for years as a stronghold of the uprising against Assad.

The Al-Assad family has ruled Syria for almost half a century, after Hafez Al-Assad, father of the current president, overthrew the government in 1971. Vast swathes of the Syrian people, inspired by the Arab Spring, rose against Bashar Al-Assad after he used deadly force to quash pro-democracy demonstrations in 2011.