Syrian government supporters in the city’s west celebrate as rebel lines fall amid reports of summary executions.

The Syrian army and its allied militias are pushing deeper into east Aleppo as rebel lines collapse and their last urban stronghold looks closer than ever to falling.

The fighters withdrew from at least six more east Aleppo neighbourhoods on Monday in the face of government advances, including al-Salheen, al-Firdous and Bustan al-Qasr, once one of the most fortified districts under opposition control.

Residents told Al Jazeera that government forces summarily executed dozens of civilians over alleged connections to opposition fighters. The figure could not be independently verified by Al Jazeera.

The Syrian Observatory for Human Rights said at least 60 people were killed by gunfire or shelling on Monday as government forces pushed into Aleppo’s remaining opposition-held districts.

“The battle of Aleppo has reached its end. It is just a matter of a small period of time, no more, no less … it’s a total collapse,” said Rami Abdel Rahman, the UK-based monitoring network’s director.

Syrian refugees in the Turkish border city of Gaziantep and the city of Istanbul, held solidarity protests on Monday night in support of the people in east Aleppo, as the government stepped up its bombardment.

Syrian state TV reported that pro-government forces were in control of 99 percent of what once was opposition-held Aleppo.

The pro-government TV network Alikbariyah Syria broadcast footage of celebrations in the streets of west Aleppo, as people handed out chocolates and congratulated each other on “the victory”.

“The joy of the people and the army are one,” said one driver, wearing military fatigues.

READ MORE: Hundreds of men from east Aleppo go ‘missing’

Earlier in the day, Lieutenant-General Zaid al-Saleh, head of the Aleppo security committee, announced in the recently recaptured neighbourhood of Sheikh Saeed that the government push to retake the entire city was in its final stages.

“The battle in east Aleppo should end quickly. They [opposition fighters] don’t have much time. They either have to surrender or die,” he said.

President Bashar al-Assad’s government’s takeover of the entire city would mark its greatest victory since the war began in 2011.

Dire conditions

Opposition fighters and tens of thousands of civilians are now confined to just a handful of neighbourhoods in the city’s southeast, including the Sukkari and Mashhad districts.

Salim Abu al-Nassar, a dentist from Bustan al-Qasr in east Aleppo, put out a video appeal on social media after fleeing to al-Ansari neighbourhood, calling for a ceasefire and describing the dire conditions in the small portion of the city left in opposition control.

Civilians are confined to a handful of Aleppo neighbourhoods [Reuters/Abdalrhman Ismail]

“Within eight kilometres square, we have over 80,000 human beings … everyone is piled on top of each other … This area may witness a real massacre if [the army] decides to move here,” he said.

“This may be my last call. I hope someone will listen somewhere around the world and relate that to their government so they can stop the shelling, the war, this madness. We hope to live. We love life. I hope we can meet again.”

Lina al-Shami, an architect and well-known social media activist from east Aleppo, also put out a “last message” on Twitter.

Syria’s state TV said on Sunday that more than 70,000 of eastern Aleppo’s estimated 275,000 residents had fled in recent days, mostly to government-held western Aleppo districts.

Scores of men who fled from the east to the west have been detained by the Syrian authorities and forced into military conscription, reports say.

READ MORE: Aleppo operation in final stages, Syrian general says

Russia’s defence ministry said on Monday that 728 Syrian fighters had laid down their weapons over the past 24 hours and relocated to western Aleppo.

The Russia-backed ground offensive, which began on November 26, followed an intensive aerial bombing campaign that knocked out most of the medical facilities, targeted civil defence and municipal vehicles and blocked roads with rubble.

The eastern Aleppo area has also been cut off from outside assistance since July by a government siege.

Opposition fighters captured the eastern half of Aleppo, Syria’s largest city and former commercial capital, in 2012.

Delayed ceasefire

The US state department said on Monday that Russia told the US it wanted a ceasefire in east Aleppo delayed for several days, a proposal the agency said was unacceptable in view of the continued attacks on civilians.

“Rather than accepting the US proposal for an immediate cessation, the Russians informed us that a cessation could not start for several days, meaning that the assault by the regime and its supporters will continue until any agreement will go into effect,” John Kirby, state department spokesman, said in response to a question about weekend talks in Geneva.

“Given the dire situation in Aleppo and the reports of continued attacks on civilians and infrastructure, this was just simply not acceptable.”

Kirby said US and Russian officials were continuing their talks in the Swiss city, although there was for now an unbridgeable gap between their positions.

“Our teams are still trying to work this out,” he said. “While we would still like to get there … I think we’re certainly at an impasse right now.”

Additional reporting by Dylan Collins