Aleppo battle: Syrian troops push deeper into rebel-held east
Syrian government forces are reported to have recaptured more parts of besieged, rebel-held eastern Aleppo, as they continue a large-scale offensive.
A monitoring group said troops had seized control of Qadi Askar and Karm al-Qaterji, hours after Karm Myassar and Karm al-Tahan were retaken.
A rebel official said the key district of Shaar was also "considered fallen".
If confirmed, that would mean the government had recaptured about 70% of eastern Aleppo in just over a week.
The UN estimates that almost 30,000 civilians have been displaced by the fighting.
More than 100,000 others may be under siege in districts still under rebel control, where food supplies are exhausted and there are no functioning hospitals.
The government's ally, Russia, is confident that it can reach a deal with the US, which backs the opposition, that would lead to the withdrawal of rebel fighters.
Russian Foreign Minister Sergei Lavrov told a news conference that talks would start in Geneva on Tuesday evening or Wednesday morning, and that a UN resolution demanding a temporary ceasefire, due to be voted on at the world body on Monday, would be counterproductive.
Meanwhile, a second Russian fighter jet has crashed while trying to land on the aircraft carrier Admiral Kuznetsov. It follows a similar incident last month. The pilots in both cases ejected safely.
The Admiral Kuznetsov is part of a group of Russian warships deployed near the Syrian coast.
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Aleppo was once Syria's largest city and its commercial and industrial hub before the uprising against President Bashar al-Assad began in 2011.
It has been divided in roughly two for the past four years. But in the past 11 months, Syrian troops have broken the deadlock with the help of Iranian-backed militias and Russian air strikes.
In early September they reinstated a siege of the east, and launched a ground assault later that month accompanied by an aerial bombardment of unprecedented scale and intensity.
On Sunday evening, the official Sana news agency cited a Syrian military source as saying that army units had retaken control of Karm Myassar and Karm al-Tahan, and entered Qadi Askar.
By Monday morning, they had taken full control of Qadi Askar and Karm al-Qaterji, according to the Syrian Observatory for Human Rights.
The UK-based monitoring group said the advances had left the key district of Shaar effectively encircled, and that troops had already taken some positions.
It reported ongoing heavy clashes there, but an official with the Jabha Shamiya rebel group told the Reuters news agency that Shaar and nearby Karm al-Jabal had effectively fallen since government forces now controlled access to them.
Other rebel-held areas also came under intense bombardment.
A correspondent for the AFP news agency said terrified residents were turning off all their lights at night-time and taking shelter in basements or entrances to buildings in the hope of remaining safe.
The Syrian Observatory says at least 319 people have been killed in rebel-held areas since the government's offensive was stepped up on 15 November, after the expiry of a three-week pause in air strikes declared by the government and its ally Russia to allow civilians and rebels to leave.
Rebel fire on government-controlled western Aleppo has reportedly killed 69 people in the same period. Sana reported that two people were killed on Monday.
On Sunday, Russian and Syrian government air strikes killed at least 73 people in rebel-held areas of the province of Idlib, south-west of Aleppo, according to the Syrian Observatory. Thirty-eight died in the town of Maarat al-Numan, it said.