Relief efforts in Fiji have been hampered after a category five cyclone downed powerlines across large parts of the Pacific island nation, aid agencies say.

Key points: Disaster officials in Fiji assess damage left behind by Tropical Cyclone Winston

Disaster officials in Fiji assess damage left behind by Tropical Cyclone Winston Elderly man was killed by a falling roof, state media says

Elderly man was killed by a falling roof, state media says Severe Tropical Cyclone Winston thought to be one of the strongest to ever hit the Southern Hemisphere

Severe Tropical Cyclone Winston thought to be one of the strongest to ever hit the Southern Hemisphere Storm has moved over Nadi and is heading out to sea

Oxfam's Raijeli Nicole said aid organisations were not able to contact each other easily as mobile phone signals and landlines were affected.

"What we need is to be able to communicate with our partners on the ground," Ms Nicole said.

"That is quite difficult right now because we've got restricted movement and that is further compounded by the fact that there is no electricity."

Disaster management officials in Fiji are assessing the damage from one of the Southern Hemisphere's most powerful storms on record, with reports of widespread devastation and one death.

There were reports entire villages were destroyed by the category-five storm — the highest possible rating — and fears for the safety of those living in remote areas.

Severe Tropical Cyclone Winston made landfall on the main island Viti Levu on Saturday, packing winds of up to 230 kilometres per hour with gusts of up to 325 kilometres per hour.

Authorities in Fiji have confirmed the death of an elderly man, marking the first fatality from the category five storm.

The man was from Nabasovi, on Koro Island, the Fiji Broadcasting Corporation reported. He died when the roof fell on him.

"Some villages have reported that all homes have been destroyed," Jone Tuiipelehaki, a communications officer for the UN Development Program, tweeted on Saturday evening.

"Fifty homes have been reported destroyed in Navaga village in Koro Island."

The Fijian Government is yet to lift a curfew which was put in place last night.

Loading

Jope Koroisavau, who lives in the tourist town of Nadi, said even sturdy houses were badly damaged.

"Massive destruction throughout, trees uprooted, houses where rooftops have been blown out," he told the ABC.

He said the main airport had some debris on the runway, but the airport itself appeared mainly intact.

Major airlines have cancelled flights in and out of Fiji's international airport in Nadi.

An assessment will be made later today about whether services will resume tomorrow.

The Fiji Times said it had received confirmation of damage to houses in Nausori, Korovou, Rakiraki, Ba, Savusavu, Taveuni and the Lau group.

"Houses have blown away, roof tops [have] gone ... power lines have been broken and debris [is] scattered around in towns and cities," the newspaper reported.

Hundreds of evacuation centres have been set up across the country, the Government said, after it declared a state of national disaster effective for 30 days, which will allow all government forces to be mobilised to help the clean up effort.

Oxfam regional director Rajeli Nicole said access to drinking water could also be an issue.

The Government also said power, water or communications outages would not be repaired until Winston passed as Fiji's Ministry of Education confirmed all schools would be closed for a week.

Bishop offers Australia's support to Fiji

Loading...

Foreign Minister Julie Bishop said the Government had offered Australia's support to Fiji.

"I have been in touch with my counterpart [in Fiji] and I have offered Australia's support and we have in place pre-position supplies in Suva that are available," Ms Bishop told ABC's Insiders.

"I have also offered the ADF to send a P-3 Orion so we can carry out aerial surveillance, particularly in the outer-lying islands and do a needs assessment.

"At this stage, I believe, the Fijian Government is coming to terms with the damage.

"We know there has been one fatality and our thoughts are with all the Fijian people at this time."

Ms Bishop said that she expects many Australians may be affected by the cyclone.

"There are about 1,300 Australians registered with the Department of Foreign Affairs and Trade, but we expect that number to be much higher," Ms Bishop said.

"It's estimated about 340,000 Australians visit Fiji every year, so we expect there are more Australians."

Opposition Leader Bill Shorten said Labor's thoughts were also with the people of Fiji and Tonga.

A storm warning remained in place for the Mamanuca group. A gale warning is in place for the Yasawa group.

A flood warning has been issued for low-lying parts of the country.

The Red Cross has warned of flash flooding along the coast in the coming days, and mudslides are also a concern.

Anyone concerned about the whereabouts of friends, or family, are urged to contact them and if they are having difficulty, to contact the 24-hour consular hotline on 1300 555 135.