Aid workers and activists inside embattled east Aleppo have pleaded for the international community to save them from what they say are arbitrary executions of non-combatants by Syrian government forces as the regime finally closes in on the rebel enclave.

The White Helmets civil defence and rescue service, as well as three other trapped aid groups operating in the city, made a final appeal for the United Nations and others to arrange a humanitarian corridor for civilians to flee the fighting late on Monday night.

“If we stay, we fear for our lives. The women may be taken to camps, the men disappeared and anyone who is known to have supported civilians will face detention or execution,” they said in a statement.

The pocket in which around 100,000 civilians and rebels are left is now less than 2.5 miles (4 square kilometres) big and suffering heavy bombardment.

"As the battle reaches new peaks and the area is plunged into chaos, thousands with no part in the violence have literally nowhere safe to run," the International Red Cross said on Tuesday, appealing for all sides to respect human life and for an immediate ceasefire.

A Syrian military source told Reuters that government soldiers and allied Iranian-backed militias were "in the last moments before victory" in Aleppo after more than four years of battle.

On the government controlled side of the city, residents celebrated the fall of the rebels - who have killed hundreds of civilians in west Aleppo in rocket attacks - with dancing and fireworks.

Several activists posted goodbye messages on Monday before going silent. "Anyone who knows anything about the Assad regime should know what to expect. Death will be a wish for those captured and deemed [to be] opposition, weather [sic] military or civil," one wrote in a Whatsapp message to journalists.

The Independent has not been able to make contact with other sources inside rebel areas since. Phone calls and texts have gone unanswered.

Videos reportedly from inside east Aleppo over the last few days show the wounded and dying lying on the streets during bombing raids, with no one left to help them. Ammar al-Selmo, head of the local White Helmets, said that his workers could hear those trapped under rubble they were unable to reach crying for help.

Dahiyet al-Assad - Aleppo Show all 16 1 /16 Dahiyet al-Assad - Aleppo Dahiyet al-Assad - Aleppo A girl who fled areas of conflict rides a vehicle in Dahiyet al-Assad, west Aleppo city, Syria REUTERS/Ammar Abdullah Dahiyet al-Assad - Aleppo Rebel fighters from the Jaish al-Fatah (or Army of Conquest) brigade have a tea in a building under construction Getty Dahiyet al-Assad - Aleppo A rebel fighters' armoured vehicle in Dahiyet al-Assad Reuters Dahiyet al-Assad - Aleppo Rebel fighters from the Jaish al-Fatah (or Army of Conquest) brigades sit on a tank Getty Dahiyet al-Assad - Aleppo Abandoned magazine of shells after rebel fighters took control of Dahiyet al-Assad Reuters Dahiyet al-Assad - Aleppo Rebel fighters ride a pick-up truck with civilians who fled areas of conflict in Dahiyet al-Assad, west Aleppo city, Syria Reuters Dahiyet al-Assad - Aleppo A rebel fighter gestures with a girl who fled areas of conflict while they ride a pick-up truck in Dahiyet al-Assad Reuters Dahiyet al-Assad - Aleppo Smoke rises near a damaged road in Dahiyet al-Assad, west Aleppo city, Syria Reuters Dahiyet al-Assad - Aleppo Syrians carry their belongings as they leave the southwestern frontline neighbourhood of Dahiyet al-,Assad Getty Dahiyet al-Assad - Aleppo A view shows a damaged minaret of a mosque after rebel fighters took control of Dahiyet al-Assad, Syria Reuters Dahiyet al-Assad - Aleppo Rebel groups have pledged to push from newly captured positions in the Dahiyet al-Assad district towards Hamdaniyeh. Rebels and allied jihadists launched a major offensive on October 28, 2016 to break through government lines and reach the 250,000 people living in the city's east Getty Dahiyet al-Assad - Aleppo Rebel groups have pledged to push from newly captured positions in the Dahiyet al-Assad district towards Hamdaniyeh Getty Dahiyet al-Assad - Aleppo Rebel fighters from the Jaish al-Fatah (or Army of Conquest) brigades hold a position at an entrance to Aleppo, in the southwestern frontline neighbourhood of Dahiyet al-Assad Getty Dahiyet al-Assad - Aleppo Smoke billows from the frontline district of Dahiyet al-Assad following an attack by rebels on Syrian regime forces in the northern city of Aleppo Getty Dahiyet al-Assad - Aleppo Syrians carry their belongings as they leave the southwestern frontline neighbourhood of Dahiyet al-Assad Getty Dahiyet al-Assad - Aleppo People who fled areas of conflict ride a pick-up truck in Dahiyet al-Assad, west Aleppo city, Syria Reuters

Unconfirmed reports from overnight on Monday also suggested that at least 79 civilians, including women and boys, had been lined up against walls by pro-government militias and shot in the neighbourhoods of Fardous and Saliheen. The UK-based Syrian Observatory for Human Rights, which uses an extensive network of sources on the ground, said that “Every hour, butcheries are carried out.”

Jan Egeland, the UN’s humanitarian adviser on Syria, tweeted that the Russian and Syrian governments would be responsible for any such abuses.

“The Gov'ts of Syria & Russia are accountable for any and all atrocities that the victorious militias in Aleppo are now committing!,” Egeland wrote.

There are already reports, confirmed by the UN’s commission for human rights, that men who have crossed into government controlled territory have gone missing, their whereabouts still unknown by their families.

Several UN, US and Russian-backed attempts to broker a ceasefire in the humanitarian crisis have failed.

Aid groups had even revised their request for three days in which to evacuate the wounded, young and elderly down from three days to three hours, to no avail.

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“We only need a temporary cessation of 60 minutes to save them all," said British surgeon Dr David Nott, who has assisted with medical training for Aleppo’s beleaguered medics via Skype.

The US State Department said Russia had turned down the proposal for an immediate ceasefire and said it could not start for several days.

East Aleppo’s supply chains were cut off in August, leaving its 250,000 residents and around 8,000 fighters - among them al-Qaeda affiliated forces - under siege conditions.

An intense Russian-backed bombing campaign since September followed by a ground assault had bought the rebel neighbourhoods to their knees.