Syria conflict: Homs aid convoy comes under fire
Renewed fighting in the city had already slowed bids to bring in relief supplies.
The Syrian Red Crescent said its vehicles were fired on, and that one of its drivers was wounded.
However, Syrian state media said four Red Crescent aid workers were wounded by rebel gunfire.
"Shots fired targeting aid trucks and the team," the Syrian Red Crescent said on its Twitter feed, without accusing anyone of being responsible, adding: "Aid truck driver injured."
A second tweet said: "Mortar shells falling in close proximity near the team and aid trucks that moved into Old City."
The UN is overseeing efforts to deliver food, water and medicine by truck to some 3,000 civilians in rebel-held areas.
The government and rebels accused each other of violating a ceasefire after mortar fire on Saturday morning delayed an earlier attempt to bring in aid.
On Friday, the first day of the agreed three-day ceasefire, more than 80 children, women and elderly people were evacuated.
Many of those evacuated on Friday looked frail and described extreme hardships inside the area, which has been under army siege for nearly a year-and-a-half.
They said bread had not been available for months, and many residents were gathering weeds and leaves to eat.
Relief officials had earlier warned that this second phase of the humanitarian operation, to allow aid into the embattled quarter, was particularly delicate, not least because the government side has always been reluctant to see supplies going in to rebel-held areas.
The BBC's Jim Muir in Beirut says it is not yet clear whether the truce breakdown is just a temporary setback, or whether it puts the whole agreement in jeopardy.
If the aid does reach the city, the next step would be another day of evacuations.
During Friday's operation, vulnerable civilians such as children, old people and medical cases were brought out of the besieged area, sometimes carried by Red Crescent volunteers.
They told journalists that there were more people trapped in the city who had wanted to leave.
Daily bombardments
Homs has been a key battleground in the uprising against President Assad.
The army launched a series of big attacks to recapture rebel areas in the Old City in the beginning of 2012, with almost daily bombardments killing thousands.
Large areas have been reduced to rubble and many neighbourhoods lie in ruins.
The situation in besieged districts of the city since June 2012 was discussed during peace talks in Geneva a week ago, but the humanitarian aid deal was actually struck between the governor of Homs and the UN resident co-ordinator in Syria.
The Syrian government is making no connection between the Homs agreement and the peace talks, but it was first mooted by the mediator there, Lakhdar Brahimi, our correspondent says.
Another round of talks is scheduled to begin on Monday and the Syrian government has confirmed it will attend.
BBC
