Pro-Assad forces seize third of east Aleppo in rapid advance

• Syrian army captures part of rebel-held east Aleppo
• Russia tells rebels to leave Syria's Aleppo by November 4 evening
• Syrian army and Russian jets halt Aleppo bombardment for second day

The speed of the advance surprised both the Syrian military and its backers as well as those who had vowed to defend opposition-held districts throughout 12 months of near constant bombardment and siege.

It also appeared to herald the denouement of the battle for control of a city that has been central to the fate of Syria, a country upended by nearly six years of civil war that has greatly destabilised the region and sparked one of the biggest exoduses of refugees anywhere since the end of the second world war.

Syrian pro-government forces stand on top of a building in the Bustan al-Pasha neighbourhood of Aleppo. Photograph: George Ourfalian/Getty Images

The ground advance was led by Iraqi militias and Lebanon’s Hezbollah, both of which have played dominant roles on the eastern outskirts as preparations for the attack intensified. The Syrian army largely played a support role, sources close to Hezbollah confirmed to the Guardian on Monday.

However, Syrian forces are stationed in greater numbers in the newly seized districts, with militia forces directed by Iran tasked with moving into remaining rebel areas.

Aid groups have said that as many as 250,000 people may still be in east Aleppo, with little access to food, water or medicine. For the first time in the past six months, large numbers of people – by some accounts as many as 20,000 – were attempting to flee on Monday. However, there was no clear route to the north or east. Up to 1,000 people had reportedly crossed into regime-held west Aleppo through the Sheikh Maqsoud district.

Residents of the east described their panic as loyalist forces advanced from the airport in the east of the city to the largely abandoned Masakan Hanano neighbourhood in the north-east.