"Between 100,000 and half a million people could be displaced as the conflict and humanitarian situation continue to worsen," said Shabia Mantoo, Yemen spokesperson for the UN refugee agency, the UNHCR.
"The humanitarian situation alone continues to worsen even without the conflict intensifying," Mantoo told AFP from the Red Sea city of Hodeida.
Fears of large-scale displacement are exacerbated by rampant food insecurity in Hodeida that the UNHCR says has reached critical levels.
The United Nations estimates more than 7,700 people have been killed and millions displaced since a Saudi-led coalition intervened in Yemen in March 2015 against Huthi rebels in support of President Abedrabbo Mansour Hadi.
The fighting has left 19 million people -- or 60 percent of the population -- struggling to find food, the United Nations says, with a third of the country's provinces on the brink of famine.