Cyclone Winston: Fiji islands. Southern hemisphere's strongest storm devastates.

At least one person is dead and entire villages are feared destroyed after the worst tropical cyclone in Fiji’s history.

Fijians, tourists and aid workers have awakened to scenes of utter destruction after a category five cyclone battered the South Pacific nation with wind gusts as strong as 325km/h and waves up to 12m high.

“The scale of the destruction is absolutely massive and it’s still far too early to tell just how many people’s homes and livelihoods have been devastated by this storm,” Australian Red Cross aid worker Susan Slattery told AAP from Suva.

“That will become much clearer over the next 24 hours and our first priority is to make sure people are safe and have the short-term assistance they need.”

An official curfew was still in place on Sunday morning and all flights in and out of Fiji remained cancelled, but the worst was believed to be over as agencies try to assess the damage.

“At the moment, we’re focused on removing fallen power lines and trees to make sure it’s safe for people to move around,” Slattery said.

“And then it’s moving into finding out whether we need shelter and clean water, and what food and hygiene items are required to keep people healthy.”

Unicef Pacific aid worker Alice Clements said Suva was spared the full force of the cyclone’s wind blasts, with the storm changing direction at the last minute when it made landfall late on Saturday.

The howling winds and driving rains that lashed the Fijian capital “paled in comparison” to what those in the eye of the storm experienced, she told AAP on Sunday.

“We’re incredibly worried about people on outer islands with weaker housing.

“We’ve seen photos of houses that have been completely flattened – there is literally nothing standing.

“These are people who were incredibly vulnerable to start with and now they’ve had potentially everything taken away from them.”

Authorities have confirmed an elderly man was killed on the island of Koro when a roof fell on him in the storm.

And there are grave fears for other people living on the island, northeast of Suva.

“Some villages have reported that all homes have been destroyed,” Jone Tuiipelehaki of the United Nations Development Program tweeted late on Saturday. “Fifty homes have been reported destroyed in the Navaga village in Koro Island.”

Power, water and communications services have been cut across much of the country of almost 900,000 people.

The Fijian government has declared a 30-day state of emergency amid concerns of flash flooding and mudslides.

Australia’s foreign minister Julie Bishop has offered Fiji assistance, including an Australian defence force P-3 Orion to carry out aerial surveillance of the outer islands for immediate needs assessment.

About 1300 Australians are registered as being in Fiji but that figure is likely to be far greater, given up to 350,000 visited Fiji every year, Bishop said on Sunday.

Cyclone Winston began to make landfall on the main island of Vitu Levu after a national curfew took effect at 6pm local time. It had earlier sunk boats and caused flash flooding on the nation’s outer islands, including Vanua Levu.

The Fijian government issued a list of 758 evacuation centres across the nation of just under 900,000 people. The country’s prime minister, Frank Bainimarama, said on Saturday that the island’s evacuation centres were operational and the government was prepared to deal with a potential crisis.

 “As a nation we are facing an ordeal of the most grievous kind,” he wrote. “We must stick together as a people and look after each other.”

The ABC quoted the prime minister expressing concerns that some people in urban areas did not appear to have heeded the warnings about the seriousness of the threat.

Save the Children Fiji’s chief executive, Iris Low-McKenzie, said the storm had the potential to cause “catastrophic damage” across Fiji, an island nation visited by hundreds of thousands of tourists every year. “We’re extremely concerned about the impact this will have on children, who are particularly vulnerable during emergencies,” she said.

The Fiji Times newspaper reported some damage, including a roof being blown off one home, from some of the nation’s smaller islands to the east as the cyclone began to strike there. It said there had been a rush of buying at supermarkets and stores as people stocked up on essential supplies.

Airlines operating in the region including Virgin Australia, Jetstar, Qantas and Fiji Airways all reported cancelled flights or altered timetables, with passengers told to consult their carrier for information.

Save the Children said it had stockpiled emergency supplies to ensure children could get back to school as soon as possible. “We have teams standing by to assess the storm damage, as well as teachers preparing to support children in emergency centres,” Low-McKenzie said.