Nearly 700 people had been taken out of the city by U.N. convoy since Friday. The three-day evacuation by the United Nations and Syrian Arab Red Crescent aid organization was intended to build trust toward a diplomatic solution to the country's nearly 3-year-old civil war.
But it was marred by mortar shells and sniper bullets that killed more than 10 civilians waiting or trying to leave, the Wall Street Journal and anti-regime activists said.
The Assad regime and opposition each blamed the other for the deadly attacks.
Some U.N. employees and an aid worker told the Journal they blamed forces loyal to the Assad regime for the attacks.
The United Nations didn't officially assign responsibility.
"It is deliberate targeting, which is unacceptable," Valerie Amos, who heads U.N. global relief efforts, told the newspaper.
The official Syrian Arab News Agency said the violence was carried out by rebels who didn't want civilians to leave.
The agreement for the operation called for three daily 12-hour cease-fires so desperately needed food and medicine could be delivered and civilians could be evacuated. The cease-fire agreement ended Sunday, the BBC reported, but both sides have suggested a three-day extension.
The Syrian government said some of those evacuated from Homs were detained after they left the city.
More than 2,500 non-combatants had been trapped in the central-western city's half-square-mile old quarter, which the opposition called the "capital of the revolution" before the siege.
"Some people were living off roots and weeds and grass and olives if they were lucky," World Food Program spokeswoman Dina Elkassaby told the New York Times.
One man whose wife died of malnutrition said he had survived on one spoon of a cereal product called bulgur daily for the past week, Elkassaby said.
Despite the weekend's events, opposition and Assad regime delegations were to meet in Geneva Monday for a second round of talks.
The first round in the so-called Geneva II talks ended 10 days ago with no substantial results.
U.N. and Arab League mediator Lakhdar Brahimi was scheduled to hold talks separately with the opposition, then with a government delegation represented by Foreign Minister Walid Muallem, Middle East Online reported.
The regime maintains the talks should focus on combating terror, while the opposition says they must pave the way for a transitional government without President Bashar Assad.
The regime says it is open to creating a transitional government but flatly rejects any rule without Assad.
Western diplomats in Geneva told the Journal they didn't believe the Homs situation would hurt the talks.
"So far, I'm not picking up any negative impact on the atmosphere in Geneva," one diplomat said.
An opposition adviser told the newspaper opposition delegates were focusing on political transition and didn't want the talks to get bogged down in arguments over what happened in Homs.