ANTAKYA, Turkey — A three-day humanitarian cease-fire in the Syrian city of Homs was supposed to be a small breakthrough, a moment of relief for civilians trapped in a grim civil war.
But mortar rounds and gunfire struck near aid convoys, damaging vehicles and leaving victims lying in the streets. Snipers fired on civilians as they fled their besieged neighborhood. Others refused to leave, fearing a massacre of those left behind. Limited food made it in, and some of the nearly 700 people who reached safety said they had been surviving on one meal a day and that some of their neighbors had resorted to eating grass.
Though few expect the international peace talks that resume in Geneva on Monday to end the war, many hope they will make life less brutal for ordinary Syrians by creating local cease-fires and opening up access to aid.
But what took place in Homs highlights the tremendous difficulties plaguing even modest humanitarian efforts, making it unlikely that the episode will emerge as a model to be repeated elsewhere.
The attacks on the aid convoys will also raise the stakes for the United Nations Security Council this week, as it weighs a draft resolution meant to force the government and rebel groups to permit aid organizations to operate.
The need for such pressure is dire, given the widespread use of siege tactics by both sides to turn hunger into a tool of war and weaken their enemies, often harming civilians as well.
The United Nations estimates that almost a third of the nine million Syrians in need are in hard-to-reach areas and that access to many of them has been deliberately obstructed. While human rights groups say the government is responsible for most of the sieges, rebels, too, have tried to starve out their enemies.
“We have entire areas of the country where the ability to transport food and other materials is severely hampered because of deliberate blockades and constraints on trucks and convoys,” Matthew Hollingworth, the director of theWorld Food Program’s Syria program, said by telephone from Homs on Sunday. “It is a tactic that everybody is using, and it has a massive impact.”
Reflecting the toll of such tactics, one older man evacuated in Homs on Sunday said he had survived on one spoon of bulgur a day for the past week and that his wife had died, malnourished and unable to get medical treatment, according to Dina Elkassaby, a spokeswoman for the World Food Program.
“Some people were living off roots and weeds and grass and olives if they were lucky,” Ms. Elkassaby said.
The Homs agreement was reached after increasingly urgent reports of hunger among the area’s estimated 2,500 residents.
Last month, a Dutch Catholic priest who has lived in the area for years issued a rare plea, saying people were hungry and needed medical care.
“There is nothing harder than seeing parents in the street looking for food for their children,” the priest, Father Frans van der Lugt, said in a video posted online.
The agreement, announced by the Syrian government last week, called for a three-day cease-fire to allow women, children and older men to leave a rebel-held part of the city while food was distributed to those who remained inside.
But the cease-fire was shaky from the start. Some residents refused to leave, fearing their departure would prompt the killing of the remaining rebels. Pro-government Facebook pages also criticized the deal and began a campaign called “No to feeding the gunmen.”
On Friday, a sniper shot an old man in the stomach as he tried to leave the neighborhood, antigovernment activists said. Still, aid groups brought out 83 people.
On Saturday, mortar rounds struck the neighborhood as a convoy was trying to enter, delaying food delivery and preventing any new evacuations.
More mortars struck on Sunday as crowds of civilians rushed to meet the convoy, killing at least six people, according to activists and videos posted online.
Later, hundreds of civilians ran between two lines of United Nations vehicles as gunfire crackled nearby. Some civilians discarded their bags as they ran.
A Homs activist, Abu Bilal, accused the government of hitting the neighborhood. “We are sure that the regime is targeting us so that it can prevent the arrival of aid into the besieged area,” he said through Skype.
The Syrian state news agency, SANA, said that “armed groups” had tried to disrupt the operation.
Mr. Hollingworth of the World Food Program confirmed that mortar rounds had struck the area and that aid vehicles had been fired on. He said that nearly 600 civilians had been brought out on Sunday and were being given medicine and food before being placed elsewhere in Homs.
The draft resolution to be considered by the Security Council this week is intended to assist such aid operations.
A leaked draft calls for the evacuation of all civilians who wish to leave besieged areas, not just women, children and the elderly, as the Syrian government stipulated in Homs. It also calls on President Bashar al-Assad’s government to stop using so-called barrel bombs — crude explosives that opposition groups say have killed hundreds of civilians in recent weeks.
It is unlikely that the council will pass a resolution that calls for those who violate international law to be held accountable, largely because Syria’s strongest international backer, Russia, would most likely veto it.
Such disagreements have long blocked unified international action in Syria, which has frustrated those who believe the Council has a duty to ease the violence and protect civilians.
“The great powers should have pushed in the right direction, all of them, and should have pushed both sides from the very beginning that there would be consequences,” said Jan Egeland, a former emergency relief coordinator at the United Nations and now president of the Norwegian Refugee Council.
Others said the limited success of the Homs operation was unlikely to build support for similar plans at the Geneva talks.
Some suggested the Syrian government had agreed to the deal only to improve its image before the talks.
“This regime has a very long history of using these humanitarian gestures to strengthen their own position,” said Steven Heydemann, the director of Syria programs at the United States Institute of Peace.