Syria conflict: Aleppo rebels pushed back by Assad's forces
Syrian government forces have retaken areas of the city of Aleppo that were lost to rebels in recent fighting.
The loss of the territory on the city's western edges was confirmed by the rebels themselves, as well as state media and UK-based monitors.
An estimated 275,000 people live under siege in the rebel-held east, where the UN says food rations are running out.
Meanwhile a Russian naval force led by an aircraft carrier is said to have moved into position off Syria.
Capt Sergei Artamonov, commander of the Admiral Kuznetsov, told Russian state media the battle group had arrived at its designated point in the eastern Mediterranean and was carrying out "joint tasks".
The naval deployment has raised fears that Russia, one of Syrian President Bashar al-Assad's closest allies in his fight against the rebels, will step up air strikes reported to have caused heavy civilian casualties.
- Why are people still living in east Aleppo?
- Life under siege in rebel-held Aleppo
- Why Assad wants to take Aleppo
'It has failed'
On 28 October, rebels and Islamist militants in Aleppo began what they called an "epic battle" to break the siege, pounding government-held areas with hundreds of missiles.
After early advances, their progress slowed but they took over several strategic points in the west of the city.
On Saturday, it was confirmed that government forces had regained control of the al-Minian district and advanced into the al-Assad district.
"The epic battle for Aleppo has failed," Rami Abdurrahman, of the British-based Syrian Observatory for Human Rights, was quoted as saying by the Associated Press news agency.
The fighting left 508 people dead, including civilians and fighters from both sides, according to his organisation.
Ninety foreign fighters were among those killed on the rebel side while 83 Syrian soldiers, 28 Hezbollah militants and 41 other fighters from Iran and Iraq were killed on the government side, the Observatory estimates.
"We fought them in every street, house, neighbourhood and schools, and they used mosques to launch attacks,'' a Syrian government commander who identified himself as Nabil told al-Manar TV, the channel run by President Assad's Hezbollah allies in Lebanon.
Zakaria Malahifji, head of the political office of the Fastaqim rebel group fighting in Aleppo, confirmed the army's advance.
"Of course, when the regime takes control, it has a negative effect, but there is persistence," he was quoted as saying by Reuters news agency.
'Rations running out'
The last remaining food rations are being distributed in rebel-held eastern districts of the city, UN humanitarian adviser Jan Egeland warned on Friday.
Without a resupply, there would be no food left to hand out next week, he said.
Mr Egeland ruled out airdrops of food, explaining that they were not possible in densely populated urban areas.
In other besieged towns like rebel-held Madaya north-west of Damascus, shortages of food, medical supplies and electricity have led to cases of severe malnutrition.
Aleppo, Syria's economic hub before the civil war began in 2011, has been divided between the two sides since 2012.
Heavy bombardment of rebel-held areas by Syrian and Russian aircraft this autumn provoked an international outcry.
Russia's air campaign in Syria, which began in September 2015 using planes mainly stationed at Hmeimim air base near Latakia, has shored up President Assad's position.
An air campaign by Western powers has focused on the Islamic State group, which controls large parts of north-eastern Syria.