Syrian forces pushed forward in Aleppo Sunday as thousands fled rebel-held areas, but they lost ground to the south where the Islamic State group recaptured the ancient city of Palmyra.
After a sudden regime withdrawal, IS jihadists made a lightning-fast advance across Palmyra, sparking new concerns for its remaining ancient treasures.
Since mid-November, forces loyal to President Bashar al-Assad have been focused on second city Aleppo, where they have retaken more than 85 percent of the one-time rebel bastion in the city's east.
On Sunday, they pounded the shrinking rebel enclave in southeast Aleppo with artillery and air strikes, seizing the Maadi district and several other neighbourhoods, a monitor said.
The Syrian Observatory for Human Rights said more than 10,000 people had fled remaining rebel-held districts since midnight, heading for government-run west Aleppo and newly retaken areas in the city's north and centre.
An estimated 120,000 people have poured out of east Aleppo since late November, the monitor said.
State news agency SANA said that on Sunday alone, at least 8,000 people had fled rebel districts through several government-run crossings.
It said approximately half were transferred to temporary shelters, while the rest were staying with relatives in west Aleppo.
An AFP correspondent in the west said air strikes on the east were less intense as night fell, but artillery fire could still be heard.
- Army withdraws from Palmyra -
US and Russian officials were expected to continue talks in Geneva Sunday on trying to reach a ceasefire in Aleppo, but intense diplomatic efforts over the past week have failed to stem the fighting.
Backing from Moscow, which began an air war in support of Assad last year, has been crucial in the Syrian army's ability to make gains nationwide.
Russian raids overnight bolstered Syrian soldiers fighting off an IS offensive on Palmyra, the renowned UNESCO World Heritage site in central Syria.
But the jihadists launched a fresh attack Sunday, the Observatory said, recapturing all of Palmyra after government forces pulled out.
"Despite the ongoing air raids, IS retook all of Palmyra after the Syrian army withdrew south of the city," said Observatory head Rami Abdel Rahman.
He said IS was "combing the city" for any remaining Syrian soldiers.
The IS-linked Amaq news agency said the group regained "full control" of the city after taking the citadel overlooking Palmyra from a strategic hilltop.
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Capturing Palmyra from IS in May was a major symbolic victory for Assad's forces -- and for its Russian ally.
Moscow has come under severe criticism in the West for its continued political and military support for Damascus as the regime pursues its assault in Aleppo.
Russia says it is consulting with the United States on the terms of an Aleppo ceasefire after a full rebel withdrawal, without any sign of an agreement so far.
- 'Yes to peace' -
Pope Francis called Sunday for an end to violence in Aleppo and across Syria.
"I appeal to all to choose civilisation: no to destruction, yes to peace, yes to the people of Aleppo and Syria," he said.
At least 413 civilians have been killed in east Aleppo since the offensive began on November 15, the Observatory said, and 139 killed in rebel rocket fire on the city's west.
The UN children's agency said all children in Aleppo were suffering from trauma.
"I have never seen in my life such a dramatic situation (as) what is happening to children in Aleppo," said Radoslaw Rzehak, UNICEF's field office head inside the devastated city.
Assad's forces retaking Aleppo appears to be only a matter of time.
The loss of east Aleppo will deal the biggest blow to Syria's opposition since the civil war began in 2011.
"We're now past the point where the opposition has any hope of pulling things back," said Yezid Sayigh of the Carnegie Middle East Center in Beirut.
Assad "will have in effect broken the back of the armed opposition... and the idea that the regime can be overcome militarily will be finally put to rest".
After meetings in Paris on Saturday, Western and Arab powers called for talks to end the war.
US Secretary of State John Kerry, who called the regime's bombings of Aleppo "war crimes", said the time was ripe for a return to negotiations.
Rebels "can still win a political settlement that honours the fight and all they've invested," Kerry said.
In a rare public appearance on Sunday, Assad attended a celebration at a Damascus mosque to mark the Prophet Mohammed's birthday, SANA reported.