Tropical Cyclone Evan has left a trail of destruction across Fiji after battering the island for more than 12 hours, destroying homes, flooding rivers and stranding thousands of tourists.

Officials say, there were no reported deaths on Tuesday as the storm headed out to sea and was downgraded a notch to category three.

Western parts of the main island of Viti Levu bore the brunt of the cyclone's fury overnight, with the Fiji Times describing the township of Lautoka as a "war zone".

The information ministry said bridges were submerged by swollen rivers, high winds toppled power lines and roads were closed by landslides and debris.

Almost 8,500 locals sheltered from the cyclone in evacuation centres, while thousands of tourists, many relocated from outlying islands for their own safety, rode out the storm in Viti Levu's resorts.

Cyclone Evan, however did not cause the same damage as Cyclone Kina, which killed 23 people when it swept through Fiji in 1993, largely due to extensive planning as the storm advanced.

Neighbouring Samoa had no advance notice when Evan pummelled it late last week and officials there said Tuesday the official death toll had risen to five, with up to 10 people still missing.

Samoa's Disaster Management Office (DMO) said almost 5,000 people were still in evacuation centres and power remained off in much of the country.

Filomena Nelson, a DMO spokesperson, said the damage caused by the storm, estimated by the government to cost $130 million, was more extensive than when a tsunami hit the country in 2009, killing 143 people.

"While the cost in lives has been less, the destruction is greater than the tsunami because it's affected a far larger area," said Nelson.