Aid teams launched fresh efforts on Tuesday to evacuate civilians from besieged districts of Syria's Homs after a truce was extended, as mutual recriminations bogged down peace talks in Switzerland.
The Syrian Red Crescent has so far helped evacuate around 1,200 people trapped in rebel-held areas of the war-ravaged central city, and delivered desperately-needed food and medicine.
In Geneva, meanwhile, the Syrian regime and opposition were due to sit down for a joint session of talks, after swapping accusations of responsibility for the violence that has devastated their country.
The opposition delegation warned late Monday it would not return for a third round of talks if no progress was made in the current session.
UN and Red Crescent teams evacuated 473 people from Homs on Monday, many of whom have spent nearly two years trapped with dwindling food and medical supplies.
They streamed out of streets rubble-strewn streets, bookmarked by half-collapsed buildings, towards the vehicles waiting to extract them from the city.
Operations to evacuate some of the estimated 3,000 people trapped in the Old City of Homs and deliver aid to those staying behind began on Friday.
The work was made possible by a tenuous three-day truce, which was extended for another 72 hours on Monday despite multiple violations, including shelling that killed 14 people and fire directed at aid convoys.
On Tuesday, a Red Crescent official said teams were preparing to resume evacuations and aid delivery.
"Civilians will be evacuated from Homs for a fifth consecutive day. A morning meeting was held with Homs governor Talal Barazi and the UN," he said.
"We are trying to reach families in the Bustan al-Diwan, where there are logistical obstacles," he added, without providing details.
Nutrition products for children
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Monday's operations did not include food delivery, but the World Food Programme said it had managed to deliver 310 family rations -- enough to feed 1,550 people for a month -- between Friday and Sunday.
It has also delivered 1.5 metric tonnes of wheat into Homs, where residents have said they survived months of a choking siege on a diet of olives and grass.
The WFP also handed out food to those escaping, including specialised nutrition products for hundreds of children.
Those leaving stood, wide-eyed, some toting backpacks in pink and blue as volunteers handed out food and escorted them to shelters.
The Red Crescent posted pictures on its Facebook page of a party that was later organised for a group of children, their faces lit up with smiles as they played with green, grey and pink balloons.
The humanitarian operation has been welcomed internationally, but UN officials and agencies have urged that the model be extended to other areas in Syria.
"I hope that those negotiating in Geneva agree to allow the sustained delivery of aid to the 250,000 people in besieged communities in Syria and all those who are in desperate need across Syria," said UN humanitarian chief Valerie Amos.
But the tone at a second round of peace talks in Geneva seemed unlikely to produce any substantive breakthroughs.
Opposition spokesman Louay Safi said the delegation was "not going to run away" from the second round, but warned that it might not attend a third round if no progress was made.
"If there is no progress at all, I think it would be a waste of time to think about a third round," he told reporters, adding that he had raised the issue with UN-Arab League mediator Lakhdar Brahimi.
On Monday, Brahimi met with the regime and opposition delegations separately, but a joint session was scheduled for Tuesday morning.
The two sides still disagree fundamentally on the purpose of the discussions, with the regime insisting they must be used to condemn "terrorism" in Syria, and the opposition seeking to discuss a transitional government and President Bashar al-Assad's departure from office.
More than 136,000 people have been killed since the conflict in Syria began in March 2011, and some 2.4 million Syrians have become refugees.