Tropical Cyclone Gene has already damaged houses on the island of Futuna in Vanuatu's south.
Cyclone Gene, which flattened houses and flooded schools and hospitals in Fiji, is now 50 kilometres east-south-east of Futuna with winds of 80 knots.
A hurricane warning is in place for the southern islands of Vanuatu and people are advised to seek shelter.
Vanuatu's Disaster Management Office says rough seas, heavy rain and flooding are likely.
Its general manager, Job Esau, says they have already received some damage reports.
"We received information that some houses have already been blown down by cyclone Gene, that is on Futuna island. We have not heard any informatuion from other islands in the southern group, like Aniwa and Aneityum. We're still making contact to those two islands as well to receive more information from them."
Job Esau says the cyclone is now moving south-south-west.