The Syrian government has reportedly sent out text messages to residents in east Aleppo warning they have 24 hours to flee before a new, intensified bombing campaign begins.

Russia announced a “humanitarian pause” on the bombing campaign against rebel-held eastern districts last week, but now the area’s 275,000 besieged residents are bracing themselves once again.

It comes as the Syrian army recaptured all of the areas towards the west of the city taken by rebel forces in a recent assault intended to break the siege.

The Syrian Observatory of Human Rights, a humanitarian watchdog, said the government had recaptured all the key areas including the western district of Dahiyat al-Assad and the village of Minyan outside the city.

The army also marched south and captured two rebel-held areas.

The reversals undo all of the progress made by the coalition of opposition fighters, who have been trying to lift the siege, which cut off a vital supply line, Castello Road, to the city in July this year.

Rebels have tried several times to break the siege, succeeding briefly in August, but no aid has entered east Aleppo since Castello Road was captured by Assad forces.

The Observatory said that more than 450 fighters and civilians had been killed since the rebels began their latest bid to break the siege on 28 October.

The dead include 215 Syrian and foreign opposition fighters, including some who carried out suicide bomb attacks, and 143 regime forces.

Nearly 100 civilians have also been killed, the majority of them in government-held west Aleppo where 30 children were among those killed in waves of rebel rocket fire.

Five civilians, including one child, were killed on Saturday in rebel shelling of government-held sectors of the city, the Observatory said.

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

Both sides have been battling for control of Syria’s second city since 2012 in what the UN called a “catastrophic” humanitarian situation.

On Thursday, the UN warned that Aleppo was down to its last food packages and faced a major risk of starvation as winter set in.