Aid workers hope to evacuate civilians trapped in Syria's besieged city of Homs Sunday, a day after the shelling of their convoy killed five residents.
The humanitarian operation, made possible by a UN-brokered local truce, was set to take place on the eve of a new round of talks between Syrian President Bashar al-Assad's regime and the rebels battling to overthrow him.
Another 300 people were killed as battles raged across Syria on Saturday, according to the Syrian Observatory for Human Rights, the latest deaths in a nearly three-year conflict that has killed 136,000 people and displaced millions.
The long-delayed humanitarian mission for Homs is entering its third day, with activists in the besieged parts of the central city fearing that Saturday's violence may affect efforts to evacuate civilians.
"We hope more aid will come in, and we hope the civilians can be evacuated, but we don't know whether that will happen," said Abu Bilal, an activist trapped by the siege.
"We are afraid that we will only see more of yesterday's shelling."
The regime and the rebels traded blame for the attack, with Homs Governor Talal al-Barazi insisting the government was committed to the truce and the aid operation "despite the (rebel) armed groups' violations."
On Friday 83 elderly people, women and children were evacuated from besieged rebel-held districts, where residents have been surviving on little more than wild herbs and olives for several months, and aid was delivered on Saturday despite the shelling of the convoy.
"Although the team was shelled and fired upon we managed to deliver 250 food parcels, 190 hygiene kits and chronic diseases medicines," the Red Crescent said on Twitter.
The operation was made possible by a surprise UN-brokered deal between the government and rebels to observe a three-day "humanitarian pause" in hostilities.
The truce -- which has so far been observed Sunday -- had eluded mediators in last month's fruitless round of peace talks in Geneva, to which the warring sides are set to return this week.
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The aid had been held up for months in a UN warehouse in a nearby government-controlled area.
The United Nations says it wants to distribute emergency rations for 2,500 people, along with medical kits, bedding, cash and other support for those leaving or choosing to stay in the Old City.
Fighting threatens aid operation
The Observatory, a Britain-based group that relies on a network of activists and other sources inside the war-torn country, said five people, including a rebel commander, were killed during Saturday's attack.
The United Nations meanwhile said it was "deeply disappointed" with the truce violations.
"I continue to call on those engaged in this brutal conflict to respect the humanitarian pause, ensure the protection of civilians and facilitate the safe delivery of aid," said UN Under-Secretary-General for Humanitarian Affairs Valerie Amos.
Homs, much of which has been reduced to rubble, was dubbed "the capital of the revolution" by activists before a bloody 2012 offensive by regime forces recaptured much of the city.
The army blockaded the remaining rebel-held areas after the assault and tightened the noose last summer by capturing the town of Qusayr, which cut off rebel supply lines to neighbouring Lebanon.
Elsewhere in the country on Saturday, some 300 people were killed, including some 20 men executed by loyalists in the central province of Hama, the Observatory said.
In the besieged Palestinian camp of Yarmuk, south of Damascus, a man and a woman died of malnutrition, it said.
Since the army blockaded Yarmuk in June last year, some 80 people have died as a result of food and medical shortages, the Observatory says.