Time is running out to get aid into Taiz, besieged by pro-Iran Houthi fighters who are preventing supplies from reaching Yemen's third-largest city, the United Nations said Friday.
Houthi fighters have encircled Taiz since early October, blocking the road that links it to Aden, interim capital of the Saudi-backed, internationally-recognised government.
"Safe, sustained and unimpeded humanitarian access is urgently needed so that essential supplies and life-saving assistance can reach people in need," said the UN humanitarian agency OCHA.
"It's 20 days and counting since Taiz has been cut off," said OCHA spokesman Jens Laerke.
"We are seeing increasingly that the fighting makes it impossible for us to get in and impossible for people to get out," he told a press conference in Geneva.
Laerke said the dwindling water supply was a growing concern, as most residents depended on water brought in by trucks.
"With the roads closed and the diesel to run the trucks very scarce, water production in the city has fallen by about half," he said.
"The cost of the truck water has roughly tripled. You can imagine what that does to these people who are trapped there."
Laerke said that while local humanitarian groups were distributing their remaining supplies, including fuel to keep water pumps and hospitals running, "it comes with a time code: the clock is running out".
"Cooking gas is another item that is largely unavailable, and the shortage is already threatening community kitchens that provide hot meals to families," he added.
Hospitals struggling: WHO
The Houthis, from Yemen's rugged north, seized the capital Sanaa in 2014, sparking a brutal civil war with a Saudi-led coalition fighting for the government.
The civil war reignited in July, months into the US-Iran conflict that has plunged the Middle East into crisis.
The World Health Organisation said hospitals in Taiz governorate were struggling to maintain life-saving services, faced with critical shortages of fuel, oxygen, medicine and medical supplies.
"With hospital services severely disrupted and stocks running dangerously low, urgent action is needed to sustain life-saving care for thousands of patients," the UN health agency's spokesman Christian Lindmeier said.
"In Taiz city alone, 42 health facilities are reporting acute shortage," he said.
Fuel shortages were threatening oxygen production, emergency transport and vaccine cold chains, he added.
The UN children's agency UNICEF said that in Taiz alone, it had screened more than 168,000 children this year, with over 52,000 found to be acutely malnourished, including more than 11,500 suffering from severe acute malnutrition -- the worst form.
The malnutrition situation "remains extremely concerning", spokesman Ricardo Pires said.