Infrastructure has been devastated across the Pacific islands that make up Vanuatu, after 250km/h winds tore through the country on Friday night.
Charity Oxfam said up to 90% of houses and almost all schools were reported to be damaged.
Oxfam country director Colin Collet van Rooyen said providing shelter, clean water and sanitation was a priority.
“This is likely to be one of the worst disasters ever seen in the Pacific,” he said.
“The scale of humanitarian need will be enormous and the proud people of Vanuatu are going to need a lot of help to rebuild their homes and their lives.
“Entire communities have been blown away.”
Oxfam executive director Helen Szoke said the charity was deeply concerned for people in Vanuatu’s harder to reach outer islands.
“These islands have much less infrastructure than the capital of Port Vila and are extremely remote and hard to reach in the best of times,” she said.
“We hold grave fears for the people on these outer and remote islands. It’s becoming increasingly clear that we are now dealing with worse than the worst case scenario in Vanuatu.”