The cyclone which formed in Tuvaluan waters got as strong as a category three system - also affecting Fiji and Tonga.
The director of Tuvalu's disaster management office, Sumeo Silu, said based on initial reports about half of the country's population had been severely affected by the cyclone.
Food security was a major concern given ocean waves, whipped up by the storm, inundated gardens and strong winds uprooted trees and damaged banana and breadfruit trees, he said.
The cyclone also damaged lifeline infrastructure including power, communications and water containment facilities.
Mr Silu said Cabinet had given the go ahead for a state of emergency but his teams were unable to travel to outer islands to carry out assessments yet.
"After that assessment, we can come with a full report [with] what is the total damage in terms of our economy and food security."
Photo RNZ Pacific Supplied / Aselu Lopati Caption: Debris across the one main road on Tuvalu's main atoll, Funafuti.