Syrian regime forces claim to have taken over two residential neighbourhoods in the rebel-held eastern part of Aleppo city in two days.

In a statement, the army said it and its allies had taken full control of the Jabal Badro district on Sunday, a day after capturing the neighbouring Hanano housing district.

The attack is likely to split the rebels' most important urban stronghold in two, weakening their control and bringing more residents closer to the frontlines.

The government's push, reportedly backed by thousands of Shia militia fighters from Lebanon, Iraq, and Iran, and the Russian air force, has laid waste to Aleppo's eastern neighbourhoods.

In pictures: Aleppo bombing Show all 14 1 /14 In pictures: Aleppo bombing In pictures: Aleppo bombing Bombing in Aleppo Smoke rises after airstrikes on the rebel-held al-Sakhour neighborhood of Aleppo, Syria April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian family runs for cover amid the rubble of destroyed buildings following a reported air strike on the rebel-held neighbourhood of Al-Qatarji in the northern Syrian city of Aleppo, on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo A man reacts as he stands on blood stains at a site hit by airstrikes in the rebel held area of Aleppo's al-Fardous district, Syria, April 29, 2016. Reuters In pictures: Aleppo bombing Bombing in Aleppo The damage of the airstrikes in the rebel-held area of Aleppo on April 28 Reuters In pictures: Aleppo bombing Bombing in Aleppo The damaged the Medecins Sans Frontieres (MSF)-backed al-Quds hospital after it was hit by airstrikes, in a rebel-held area of Syria's Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo Syrians evacuate an injured man amid the rubble of destroyed buildings following an air strike on a rebel-held of Aleppo on April 29, 2016. AFP/Getty Images In pictures: Aleppo bombing Bombing in Aleppo People inspect the damage at a site hit by airstrikes, in the rebel-held area of Aleppo's Bustan al-Qasr AP In pictures: Aleppo bombing Bombing in Aleppo A man leads a woman in tears and child out of the scene after airstrikes hit Aleppo AP In pictures: Aleppo bombing Bombing in Aleppo Civil defence members search for survivors after an airstrike at a field hospital in the rebel held area of al-Sukari district of Aleppo Reuters In pictures: Aleppo bombing Bombing in Aleppo A Syrian boy is comforted as he cries next to the body of a relative who died in a reported air strike in the rebel-held neighbourhood of al-Soukour in the northern city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo A Syrian family walks amid the rubble of destroyed buildings following a reported air strike in the Bustan al-Qasr rebel-held district of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers and rescuers remove a baby from under the rubble of a destroyed building following a reported air strike on the rebel-held neighbourhood of al-Kalasa in the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrians help a wounded youth following an air strike on the Fardous rebel held neighbourhood of the northern Syrian city of Aleppo Getty Images In pictures: Aleppo bombing Bombing in Aleppo Syrian civil defence volunteers evacuate people from a damaged building following a reported airstrike in the rebel-held neighbourhood of Tareeq al-Bab in the northern city of Aleppo

"The situation in besieged Aleppo [is] very very bad, thousands of eastern residents are moving to the western side of the city," said Khaled Khatib, a photographer for the Syrian Civil Defence search-and-rescue group, better known as the White Helmets.

"Aleppo is going to die," he posted on Twitter.

Hundreds of residents of eastern Aleppo fled the shifting frontlines ahead of the army's advance.

The UK-based Syrian Observatory for Human Rights said around 400 people had travelled into Hanano, where the army transferred them to government-held western Aleppo.

The Observatory says the assault has killed at least 219 civilians, including 27 children.

An estimated 275,000 people are trapped in wretched conditions in the city's rebel-held eastern districts since the government sealed its siege of the enclave in late August.

Food supplies are running perilously low, the UN warned on Thursday, and a relentless air assault by government forces has damaged or destroyed every hospital in the area.

Boy asks if he will die after alleged chlorine attack in Aleppo

The UN's child agency warned on Sunday that nearly 500,000 children were now living under siege in Syria, cut off from food and medical aid, mostly in areas under government control. That figure has doubled in less than a year.

Many are now spending their days underground, as hospitals, schools and homes remain vulnerable to aerial bombardment.

"Children are being killed and injured, too afraid to go to school or even play, surviving with little food and hardly any medicine," said Unicef executive director Anthony Lake.

"This is no way to live – and too many are dying."

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The assault came as activists reported tens of civilian casualties from a presumed regime or Russian air strike on a village outside of Aleppo.

The Local Coordination Committees activist network in Syria reported 15 civilians killed in a Russian air strike on the village of Anjara, controlled by the opposition in the western Aleppo countryside, and many others wounded.

Activists usually identify planes by their silhouettes and home base.