Syrian rebels vow to resist army advances in Aleppo

• Syrian army captures part of rebel-held east Aleppo
• UN envoy sees continued US work to end Syria war
• Reconciliation agreements signed with 6 more Syrian settlements — Russian Defense Ministry

Gains by the Syrian army and its allies since last week have brought whole districts back under government control and led to a human exodus as thousands have fled their pulverized neighborhoods near the rapidly shifting front lines.

A Syrian government soldier rides a military vehicle near a mosque, after taking control of Aleppo's Al-Haidariya neighbourhood, Syria in this handout picture provided by SANA on November 28, 2016. SANA/Handout via REUTERS

With the rebels now reduced to an area just kilometers across, the leaders of Russia and Turkey, two of the most powerful supporters of the opposing sides in the war spoke by phone on the need for a ceasefire, according to sources in Ankara.

The army and its allies said they had taken the Sheikh Saeed district in the south of the city on Wednesday. Rebels denied this, saying the government's advance had been repelled. The Syrian Observatory for Human Rights, a British-based monitoring group, said the insurgents retained a third of Sheikh Saeed.

The Observatory reported that the government was detaining and questioning hundreds of those fleeing rebel-held areas for the comparative safety of state-controlled districts.

A Syrian military source denied this, saying there had been no arrests, but adding that displaced people whose identities were not known were being moved into "specific places" in the areas of Aleppo where fleeing civilians were found.

In their attack on Wednesday, government forces stepped up the use of air strikes, including in Aleppo's Old City, according to a rebel official. Rescue workers in eastern Aleppo said 45 people were killed in an artillery bombardment.

The U.N.'s aid chief, Stephen O'Brien, told a Security Council emergency meeting on Aleppo that dozens of humanitarian staff were trapped in Aleppo and that warring parties must protect civilians before the city becomes "one giant graveyard".

After a year of gradual advances for Syrian President Bashar al-Assad, backed by Russia, Iran and Shi'ite militias, the taking of Aleppo would represent a huge stride forwards in his efforts to end the rebellion after nearly six years of conflict.

For the mostly Sunni Muslim rebel groups, the fall of Aleppo would deprive them of their last big foothold in a major city. A leadership council of the rebel groups in Aleppo called on all men able to bear arms to "defend the oppressed".

Russian air force has pounded rebels for more than a year, said it hoped the Aleppo situation could be resolved by the end of the year. Rebels in the city have vowed no surrender.