The Fiji meteorological service says tropical cyclone Ula is now a category three storm.
It says the system, which became a three overnight, is moving north-west at three kilometres per hour.
A storm warning is currently in force for ships within 500 kilometres of Ula, as it moves between Fiji and Vanuatu.
Cyclone Ula is expected to reach the southernmost islands of Vanuatu on Monday.
Source:
Radio New Zealand International