Syrian forces pushed forward in Aleppo on Sunday as thousands fled rebel-held areas, but they lost ground to the south where Islamic State of Iraq and the Levant (ISIL) terrorist group recaptured the ancient city of Palmyra.

After a sudden government withdrawal from Palmyra, ISIL militants made a lightning-fast advance across the town, sparking new worries for remaining ancient treasures at its UNESCO World Heritage site, The National, a government-owned English-language daily newspaper published in Abu Dhabi, United Arab Emirates, reports.

Since mid-November, forces loyal to President Bashar Al Assad have been focused on the second city of Aleppo, where they have retaken more than 85 per cent of the formerly rebel-held east.

On Sunday, they pounded the shrinking rebel enclave in south-east Aleppo with artillery and air strikes, seizing the Maadi district and several other neighborhoods, an opposition monitoring group said.

The Britain-based Syrian Observatory for Human Rights said more than 10,000 people had fled the remaining rebel-held districts since midnight, heading for government-held west Aleppo and newly retaken areas in the city’s north and center.

An estimated 120,000 people have poured out of east Aleppo since late November, according to the Observatory.

State news agency Sana said that on Sunday alone, at least 8,000 people had fled rebel districts through several government-run crossings.

Approximately half were transferred to temporary shelters, it added, while the rest were staying with relatives in western Aleppo.