Aid officials have rushed to evacuate more women, children and elderly people from rebel-held areas blockaded by government troops for more than a year in Syria's third-largest city after a United Nations-brokered ceasefire was renewed for three more days.
The truce in Homs, which began on Friday, has been shaken by continued shelling and shooting that prevented some residents from escaping and limited the amount of food aid delivered into besieged neighbourhoods.
UN humanitarian chief Valerie Amos sharply criticised the two sides, saying UN and Syrian Red Crescent workers were "deliberately targeted".
The drama in Homs, where Baroness Amos said around 800 civilians had been evacuated so far, played out as activists yesterday reported new sectarian killings in Syria's civil war.
Al Qaida-inspired rebels killed more than two dozen civilians, including an entire family, when they overran a village populated by minority Alawites on Sunday, Rami Abdurrahman of the British-based Syrian Observatory for Human Rights said. They also killed around 20 local fighters in the village.
The violence further rattled peace talks that entered their second round in Geneva - and which quickly became mired in recriminations between President Bashar Assad's government and the opposition in exile.
The two sides' first face-to-face meetings adjourned 10 days ago, having achieved little. This time, the two appeared even further apart, with no immediate plans to even sit at the same table. UN-Arab League envoy Lakhdar Brahimi was holding separate talks with each side.
"The negotiations cannot continue while the regime is stepping up its violence against the Syrian people," opposition spokesman Louay Safi said after talks with Mr Brahimi. The opposition insists the talks' aim is to agree on a transitional governing body that would replace Assad.
But Syrian deputy foreign minister Faisal Mekdad said the issue of Assad stepping down was not on the agenda. "Please tell those who dream of wasting our time here in such a discussion to stop it," he told a reporter.
The events of the past few days have only underscored each side's position. The government says it is trying to defeat an extremist, al Qaida-style insurgency. Syria's opposition, in turn, points to government blockades of dozens of rebel-held areas that have caused widespread hunger and sickness among civilians as proof of the cruelty of Assad's rule.
The aid operation in Homs laid bare the desperation in the besieged areas. Homs, in central Syria, was one of the first cities to rise up against Assad and while government forces have retaken much of the city, several rebel-held districts in its historic old centre have been under a suffocating siege for more than a year.
Many of those evacuated since Friday "were traumatised and weak", Baroness Amos said. They reported "terrible conditions at the field hospital in the Old City, where the equipment is basic, there are no medicines and people are in urgent need of medical attention".
She said around 800 had been evacuated since Friday, though the governor of Homs province put the number at around 1,070, including 460 evacuated yesterday. Under the UN-brokered truce, the government refused to allow males between 15 and 55 to leave, presuming them to be fighters. Those leaving are women, children and elderly.
Baroness Amos said the truce had been extended for three days. The original truce ran from Friday to Sunday, but the continued shelling and shooting between the two sides severely limited efforts. Eleven people were killed by the fighting.
Over the weekend, some women and elderly tried to leave but were unable to make their way through checkpoints to evacuation buses, according to Khaled Erksoussi, the head of operations of the Syrian Red Crescent.
He said some food aid was brought into the areas over the weekend - "but not the quantity we had hoped for" - and none made it in yesterday.
On Sunday people rushed through gunfire to reach UN vehicles carrying food that did make it in. Then they fought over the oil, sugar and other supplies, according to one activist in Homs.
"They didn't care about death; the hunger was killing them," he said.
At the United Nations, Russia threatened to veto Western efforts to push through a Security Council resolution that would raise the prospect of sanctions against Syria unless the government gives unrestricted access to deliver humanitarian aid.
Neither Russia's UN ambassador Vitaly Churkin nor China's ambassador attended a meeting to discuss the Western and Arab-backed resolution.
The proposed resolution puts most of the blame for the humanitarian crisis on the Syrian government.
Meanwhile, a third batch of Syria's chemical weapons material was shipped out of the country on a Norwegian cargo vessel, the Organisation for the Prohibition of Chemical Weapons said.
The Hague, Netherlands-based OPCW, which is overseeing Syria's attempts to destroy its chemical weapons, said an unspecified amount of chemicals used in making weapons had also been destroyed inside Syria.
Syria has missed several deadlines on the timetable to have its chemical weapons eradicated by June 30 but insists it will meet the final deadline.