Over 45,000 people are fleeing their homes as Houthi forces push to usurp Marib, the city that has seen around 1 million people flee since late 2014.
The number of displaced people in camps in Yemen's Marib province has risen nearly 10-fold since September, with over 45,000 people fleeing their homes as Houthi forces press an offensive.
Conditions at 137 displacement sites are poor and deteriorating, the United Nations migration agency said on Wednesday.
The International Organization for Migration, IOM, called for more funding and warned of a larger exodus should fighting reach Marib city, the capital.
"We've not witnessed this much desperation in Marib in the last two years as we have in the last two months," said IOM Yemen chief representative Christa Rottensteiner.
"Communities are being repeatedly displaced and arriving at our sites in dire need," Rottensteiner said, adding that up to 40 people sometimes share one small tent.
The Iran-aligned Houthis have advanced on most districts in energy-rich Marib, which is the internationally recognised Yemen government's last stronghold in the country's north.
Marib city is home to three million people, including nearly 1 million who fled other parts of Yemen after the Houthis ousted the government from the capital, Sanaa, in late 2014.
Rottensteiner expressed IOM's concerns over "the prospect that hundreds of thousands of people might be forced to move again if violence reaches the city."
There are also concerns of "rising civilian casualties and the destruction of civilian infrastructure."
IOM said this year's $3.85 billion aid response plan is only 57% funded, and that the agency itself has received only half its requested $170 million.