"We have been unable to distribute food in Yarmuk for over a week now, which is potentially disastrous for the besieged civilians there, trapped by the conflict and desperately dependent on UNRWA," spokesman Chris Gunness said.
"UNRWA strongly appeals to the authorities and all concerned parties to allow the agency immediate and unrestricted humanitarian access to the civilian population inside Yarmuk."
Much of the once-bustling Yarmuk camp, which was home to both Syrians and Palestinians, has been reduced to rubble by fighting, and just 18,000 Palestinians now remain of the 1,50,000 who lived there before the conflict.
After a deal reached in late December, UNRWA began distributing aid in the camp on January 18.
More From This Section
Gunness said some 6,500 food parcels were handed out between then and February 7, when clashes erupted in the camp and distributions were halted.
"Those provisions will now be running out for those people fortunate enough to receive them," he told AFP.
"The humanitarian needs of Yarmuk's civilians remain enormous and UNRWA will continue to press all concerned to ensure that food deliveries are urgently resumed.