Damage caused by Harold near Vanuatu's capital Port Vila is shown on Tuesday. The storm is now moving towards Fiji.— AFP/VNA Photo

SUVA — A deadly Pacific storm slammed into Fiji on Wednesday, tearing off roofs and flooding towns, after leaving a trail of destruction in the Solomon Islands and Vanuatu.

Tropical Cyclone Harold weakened slightly overnight from a scale-topping Category Five to a Four, but was still lashing Fiji with winds of up to 240 kilometres per hour (150 miles per hour), forecasters said.

The official NaDraki weather service said the cyclone was offshore south of Fiji's main island Viti Levu, but passing closer to land than initially expected.

Despite the downgrade, it said Harold remained "extremely dangerous" and advised residents in the island's south to shelter in churches, schools or other substantial buildings.

Images on social media showed extensive damage at Nausori, just outside Suva, with corrugated iron roofs peeled back by the ferocious winds.

The main street of Ba, in the island's north, was submerged after the local river burst its banks.

The National Disaster Management Office said residents along much of the south coast, home to many of the country's major tourist resorts, should evacuate.

"We are expecting a significant storm surge to be very dangerous for those living in coastal areas, we urge you to move to higher ground," it said.

NDMO director Vasiti Soko said evacuation centres had been set up and officials were attempting to maintain social distancing to ensure COVID-19 did not spread among those fleeing the cyclone.

Fiji has 15 cases of the coronavirus, with all known sufferers in quarantine before the cyclone hit.

Town 'obliterated'

Harold claimed 27 lives in the Solomon Islands last week, and on Tuesday tore through Vanuatu, destroying much of the country's second-largest town Luganville.

World Vision's Vanuatu director Kendra Gates Derousseau said an aerial survey carried out by disaster officials late Tuesday showed the town of Melsisi on Pentecost island had also been devastated.

"We've done some programming there in the past, so I can recognise the landmarks - you can see that 90 per cent of all buildings are obliterated, is the term I'd use," she said.

A massive international aid effort was launched after the last Category Five storm to hit Vanuatu, Cyclone Pam in 2015, flattened the capital Port Vila.

But Vanuatu's international borders are currently closed as the impoverished Pacific nation bids to remain one of the world's few places with no confirmed COVID-19 cases.

The government has revoked a domestic travel ban imposed as part of its virus response, which will allow disaster relief to flow from Port Vila to the worst-hit islands in the north.

New Zealand said it had deployed a P-3 Orion aircraft to help with damage assessments and allocated NZ$500,000 (US$300,000) in aid funding for essential supplies.

Foreign Minister Winston Peters said Wellington would provide further assistance if requested by Vanuatu.

"We are aware that the Government of Vanuatu is running a 'keep it out' strategy, and we will give serious consideration to ensure that any response to the Cyclone does not lead to the spread of COVID-19 to Vanuatu," he said.

The cyclone formed off the Solomons last week, where it washed dozens of passengers from an inter-island ferry into the sea.

It was initially expected to only reach Category Three.

Latest forecasts say it will brush past Tonga early Thursday, still at Category Four strength, before petering out over the sea by the weekend. — AFP