SUVA, Fiji - Fiji's government Tuesday declared a state of disaster as the first deaths were reported in the cyclone-ravaged Pacific nation where 17,000 people have fled to evacuation centres.

The leader of the military regime, Voreqe Bainimarama, said although the full extent of the damage from Cyclone Tomas was yet to be determined, it had been devastating.

"It is evident that wherever Tomas has struck, the damage has been overwhelming," he said in a statement.

There were unconfirmed reports of "a few" deaths in the devastating category four cyclone -- said to be the worst in living memory -- which struck Fiji's eastern Lau group of islands Tuesday, National Disaster Management Office director Pajiliai Dobui said.

"I think some lost their lives but it is just a few," Dobui told AFP.

"What we have been hearing from some of the islands is the devastation and the wind and the storm surges were too much," Dobui said.

Dobui said he did not have further information on the reported fatalities, which required confirmation by police, but reports from islands suggested Cyclone Tomas was the worst in living memory.

"Those who have experienced other cyclones say this is the longest and the strongest they have come across -- and the most destructive," he said.

The only confirmed death from the cyclone was of a woman who drowned in rough seas off the second-largest island of Vanua Levu as the cyclone approached at the weekend.

Cyclone Tomas cut a swathe of destruction through the north and east as winds averaging 175 kilometres (109 miles) an hour lashed the Pacific island group for a second day Tuesday.

The main island of Viti Levu was spared the worst of the devastation but there were reports of extensive damage from Vanua Levu and the eastern outlying islands, officials said.

Some villages in coastal areas had been inundated by waves caused by storm surges, Dobui said.

A state of disaster was declared in the north and east of Fiji after the National Disaster Council, chaired by Bainimarama, met Tuesday to assess early damage reports, National Disaster Management Office operations officer Anthony Blake said.

He told reporters 73 houses had been confirmed damaged in the north but the number was expected to rise sharply.

The full extent of the devastation was still unclear as communication links with many of the smaller islands and isolated areas on Vanua Levu remained cut Tuesday.

Electricity remained out in many parts of Vanua Levu, and water and sewerage services were also affected.

More than 17,000 people had fled to evacuation centres by Tuesday -- mostly in the north of the country -- as the storm damaged buildings and crops, cut communications and power and flooded low-lying areas.

On Gau island to the east of Viti Levu, Lamiti village headmaster Solomone Rasiga told Fiji commercial radio villagers sheltered overnight from fierce winds and heavy rain.

"The wind is very strong, there is a lot of damage to crops," he said.

Houses near the sea had been badly damaged and some small houses and outbuildings near a river had been washed away, he said.

Cyclone Tomas was expected to gradually weaken and pass Fiji's southernmost island around midnight, the Fiji Meteorological Service said.

Schools and government offices remained closed Tuesday and a curfew was extended until early Wednesday for all areas except the western region of Viti Levu.

The international airport at Nadi, in Viti Levu's west, reopened Tuesday although domestic air and shipping services remained suspended.