The Syrian army and its allies are in the "final stages" of recapturing Aleppo after a sudden advance that has pushed rebels to the brink of collapse in a shrinking enclave, a Syrian general says.
A Reuters journalist in the government-held zone said Monday's bombardment of rebel areas had continued non-stop overnight, and a civilian trapped there described the situation there as resembling Doomsday.
"The battle in eastern Aleppo should end quickly. [The rebels] don't have much time. They either have to surrender or die," Lieutenant General Zaid al-Saleh, head of the government's Aleppo security committee, told reporters in the recaptured Sheikh Saeed district of the city.
Pro-government forces were clashing with insurgents in the Fardous district, which was at the heart of the besieged pocket only days ago, after taking Sheikh Saeed in the south and Saliheen in the east, a rebel official said.
"The situation is extremely difficult today," said Zakaria Malahifji of the Fastaqim rebel group fighting in Aleppo.
The rebels' sudden retreat represented a "big collapse in terrorist morale", a Syrian military source said.
Syrian President Bashar al-Assad, backed by Russia, is now close to taking back full control of Aleppo, which was Syria's most populous city before the war and would be his greatest prize so far after nearly six years of conflict.
The Russian Defence Ministry said since the start of the Aleppo battle, more than 2200 rebels had surrendered and 100,000 civilians had left areas of the city that were controlled by militants.
"People run from one shelling to another to escape death and just to save their souls ... It's doomsday in Aleppo, yes doomsday in Aleppo," said Abu Amer Iqab, a former government employee in the Sukkari district in the heart of the rebel enclave.
While Aleppo's fall would deal a stunning blow to rebels trying to remove Assad from power, he would still be far from restoring control across Syria. Swathes of the country remain in rebel hands, and on Sunday Islamic State retook Palmyra.
Tens of thousands of civilians remain in rebel-held areas, hemmed in by ever-changing front lines, pounded by air strikes and shelling, and without basic supplies, according to the Syrian Observatory for Human Rights, a British-based monitoring group.
Rebel groups in Aleppo received a US-Russian proposal on Sunday for a withdrawal of fighters and civilians from the city's opposition areas, but Moscow said no agreement had been reached yet in talks in Geneva to end the crisis peacefully .
The rebel official blamed Russia for the lack of progress in talks, saying it had no incentive to compromise while its ally Assad was gaining ground.
"The Russians are being evasive. They are looking at the military situation. Now they are advancing," he said.
The Observatory said the Sheikh Saeed district had fallen to the army in fighting on Sunday night and early on Monday and troops were firing on the districts of Karam al-Daadaa and Fardous.
An advance into those districts would take the army into the heart of the area held by rebels as recently as Saturday, pushing them towards a last bastion of control on the west bank of Aleppo's river and the area southwest of the citadel.