UNICEF says an estimated 16,000 people in Vanuatu face immediate hunger and lack of safe water after the destruction caused by Cyclone Vania two weeks ago.
The storm hit mainly the islands of Tanna and Erromango.
A joint assessment by the government, UNICEF and partners has revealed an almost complete destruction of crops on the islands, leaving families without food or incomes for the next six months.
Damage to water systems and extensive flooding in some areas has raised concerns over access to clean water.
With ground wells contaminated and health centres impacted, UNICEF warns of the risks for disease outbreaks.
It says parts of the area were already experiencing food shortages due to a drought earlier in the year and heightened vulnerability because of ash falling from Mt. Yasur volcano.