Relief groups in Yemen's third city Taez said Monday that humanitarian aid was not reaching the provincial capital under rebel siege.
"No aid has arrived in the besieged city," a member of a local medical relief committee told AFP.
"We heard there is aid entering areas outside the city... controlled by those besieging us," Mohammed al-Qobati said.
The World Health Organization said last week it had managed to deliver more than 100 tonnes of medical aid in Taez province to benefit more than a third of "3 million people... in dire need of humanitarian assistance".
But the delivery of 22 tonnes of medical aid to five health facilities in Taez city was "on hold due to access issues," it said.
"There is a lack of medicine and oxygen cylinders," Qobati said. "Taez is living a real catastrophe."
The southwestern city's largest hospital, Al-Thawra, closed on Friday after running out of medical supplies and surgical equipment.
Its 600,000 residents are in desperate need and many have taken to treacherous mountain paths to bring in essential goods.
They have been caught in the crossfire between loyalists to Yemeni President Abedrabbo Mansour Hadi who are defending their positions in Taez and Shiite Huthi rebels who have encircled them.
Abdulkarim Shamsan, the head of a coalition of local aid groups, said the city had also not received any food supplies.
"The aid is being given away to those who are killing us," Shamsan told AFP.
"The militias have tightened the noose on Taez, stopping the entry of people on foot and confiscating anything they are carrying," he said.
The conflict in Yemen has escalated dramatically since Saudi-led air strikes began in March, with more than 5,800 people killed and 80 percent of the population in need of humanitarian aid.