The Syrian army recaptured a major district of Aleppo on Monday, leaving rebel fighters cornered in a small pocket as the battle for the city entered its "final phase".
President Bashar al-Assad's forces held more than 90 percent of the onetime opposition stronghold of east Aleppo, a monitor and military official said, and appeared on the verge of retaking the entire city.
A Syrian military official in Aleppo told AFP the "operation in eastern neighbourhoods is entering its final phase", as fierce clashes were reported in the few districts of the city left under rebel control.
The fall of Aleppo would deal the rebels their worst defeat since the beginning of Syria's conflict in 2011, and leave the government in control of the country's five major cities.
The Syrian Observatory for Human Rights monitoring group reported early on Monday that the army had captured the large Sheikh Saeed district in southeast Aleppo.
Syrian official media confirmed the retaking of Sheikh Saeed, with state television showing what it said was live footage from the neighbourhood.
Only the districts of Mashhad and Sukkari remained fully under opposition control, said the Britain-based Observatory, with others divided between the opposition and advancing army troops.
"The areas still under opposition control are very small, and they could fall at any moment," Observatory director Rami Abdel Rahman said.
Overnight and into Monday morning, government warplanes and artillery pounded the remaining rebel-held territory in the east of the city.
An AFP correspondent in the government-held west of Aleppo said the bombardment could be heard from there and was some of the heaviest in recent days.
Terrified residents have poured out of rebel-held neighbourhoods as the army advanced since beginning its operation on November 15.
The Observatory said Monday another 10,000 people had fled rebel areas in the previous 24 hours, bringing the total number of those who have left -- mostly to government-held territory -- to 130,000.
On Sunday alone, state news agency SANA said, 8,000 people fled rebel districts through government-run crossings.
It said about half were transferred to temporary shelters, while the rest were staying with relatives in west Aleppo.
And at least 3,500 civilians left east Aleppo neighbourhoods on Monday, SANA reported.
Syria's rebels seized control of east Aleppo in 2012, a year into an uprising that began with anti-government protests but spiralled into a civil war after a regime crackdown.
The war has become a complex multi-front conflict, drawing in proxy powers and jihadists like the Islamic State group, which on Sunday overran the city of Palmyra nine months after being expelled.
IS began a new offensive in the desert east of Homs province last week, seizing government positions and oil fields before advancing on Palmyra.
It was briefly forced back from the city early Sunday, after heavy Russian air strikes and the arrival of Syrian troop reinforcements.
But despite the efforts, the Observatory said Sunday afternoon that the group had recaptured all of the city.
IS held Palmyra between May 2015 and March 2016, carrying out a campaign of destruction against ancient ruins in the city that are a UNESCO World Heritage site.
On Monday, the jihadists were advancing south and west of Palmyra, fighting with the army near the town of Al-Qaryatain, the monitor said, as Russian warplanes carried out fresh strikes.
Four civilians, including two children, were killed by IS gunfire in the city as the group carried out "clearing operations" on Sunday, the Observatory said.
After taking control of the city, IS also carried out execution-style killings of eight people accused of being regime fighters or supporters in Palmyra, it said.
More than 300,000 people have been killed in Syria's war, and over half the country displaced.
The government assault on Aleppo has killed at least 415 civilians since mid-November, according to the Observatory. Another 130 civilians have been slain in rebel fire on the west of the city in the same period, it says.
Diplomatic efforts to bring an end to the conflict have repeatedly failed.
Russia last week said talks were underway with US officials on securing a ceasefire in Aleppo and the withdrawal of all rebel forces from the city.
But despite a series of high-level meetings there was no progress in halting the fighting.