The head of the Red Cross in the Federated States of Micronesia says 60 to 80 percent of homes on Weno, the capital of Chuuk State, were destroyed by Typhoon Maysak, which has left up to 6000 people displaced.
Chuuk was the first Micronesian state to be struck by the typhoon, which was upgraded to a category five super-typhoon as it approached neighbouring Yap State, where it is feared damage has been extensive.
Isao Frank said volunteers have been mobilised in Chuuk to begin the clean-up and distribute relief supplies.
Mr Frank said crops and infrastructure have been destroyed and most of the population of Weno has been displaced.
"They're estimating that around - this is in Chuuk - that around 830 dwellings have been destroyed and we're looking at around 6000 folks being displaced, just from their situation reports."
Mr Frank said evacuation centres, which have been set up in schools and churches, were overcrowded, and people were awaiting the arrival of government ships carrying relief supplies this weekend.
Yap badly hit
Assessments carried out by authorities in the state of Yap have revealed massive devastation in the atolls that bore the brunt of the super-typhoon this week.
Yap Lieutenant Governor James Yangetmai said a plane carried out an assessment yesterday of the three atolls worst hit by Typhoon Maysak - Fais, Ulithi, and Faraulep - and reported extensive damage but no fatalities.
Mr Yangetmai said crops have been wiped out, water supplies contaminated, and all buildings except those built from concrete have been wiped out.
"The only remaining are those that were built of concrete, which are very few of them. On one island, they reported that only four structures were built of concrete and even with that, their roof flew off."
He said there was an urgent need for shelter, food and water for the atolls' residents and further assessments were hoped to be carried out this weekend.
But he said it could take days to get relief supplies to the atolls worse-affected by Maysak.
Mr Yangetmai said a government vessel deployed from Pohnpei hoped to reach the atolls this weekend before supplies ran out.
"We're hoping that by Saturday water will reach the island of Faraulep. I think they said four, four water tanks they were able to protect from flying debris. We hope those four water tanks have water in them and could sustain them at least up 'til Saturday or Sunday."
UN concerned at extreme weather events
The head of the UN Office for Disaster Risk Reduction, Margareta Wahlström, has expressed her concerns about the future development of Small Island Developing States in the face of extreme weather events.
Ms Wahlström says it is remarkable that in the two weeks since the World Conference on Disaster Risk Reduction, both Vanuatu and the Federated States of Micronesia have been forced to declare a state of emergency following two separate Category 5 cyclones.
Ms Wahlstrom says for many small island states, expected future losses are not just disproportionately high, they pose an existential threat.
She says the Pacific is a constant reminder to the rest of the world of what is at stake.
She says this year an agreement is sought on climate and new sustainable development goals to complement the framework on disaster risk reduction agreed last month in Japan.