Parts of Vanuatu are being warned to expect gusts to 235 kilometres an hour as category 5 Severe Tropical Cyclone Harold bears down on the island nation.

About 7am Monday (NZT) the Vanuatu Meteorology and Geo-Hazards Department said the tropical cyclone was about 100km west of Luganville - on the large northern island of Espiritu Santo - and moving east at 18kmh.

Hurricane force winds of 215kmh, gusting to 235kmh within 37 kilometres from the centre were expected to affect some provinces in the following 12 to 24 hours. Maximum sustained winds close to the centre of the cyclone were estimated at 215kmh.

During Monday, the hardest hit province could expect destructive storm force winds of 120kmh with gusts to 150kmh within 74km of the cyclone centre.

"Damaging gale force winds, destructive storm force winds and hurricane force winds with heavy rainfalls and flash flooding over low lying areas and areas close to river banks including coastal flooding is expected over Sanma, Torba, Penama, and Malampa provinces today," VMGD said on Monday morning.

"Very rough to phenomenal seas with heavy to phenomenal swells are expected over northern and central open and coastal waters today as the system continues to move closer to the Islands of Vanuatu," it said.

"People, including sea going vessels are strongly advised not to go out to sea within affected area until the system has moved out of the area."

The latest forecast track map from Fiji's Nadi Tropical Cyclone Warning Centre showed the centre of the cyclone at Category 3 strength passing to the south of Fiji later on Tuesday.

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