A state of emergency was declared in Fiji Sunday as severe storms brought widespread flooding with at least six people feared dead.

Thousands were evacuated from their homes and those living in low-lying areas were advised to move to higher ground as rivers burst their banks.

Tourists in the popular resort area of Denarau Island were trapped after the only road to the airport was inundated.

Interim Prime Minister Voreqe Bainimarama declared the state of emergency on the recommendation of the National Disaster Management Office (Dismac), Interim National Security Minister Epeli Ganilau said.

"It is basically to safeguard lives and property. We want to prevent criminal elements from taking advantage of the flood hit areas," Ganilau told the Fijilive website.

The suspected death toll was six and police warned of the risk of more fatalities as they pleaded with parents to prevent children swimming in the flooded rivers and creeks.

In the village of Malabi the body of a 19-year-old was found, with two girls missing and believed dead after being caught in a landslide.

In Ba, a 31-year-old man died after he was washed away by strong currents while elsewhere in Fiji searches were under way for at least two children swept away in flood waters.

Police imposed curfews in the flood-ravaged towns of Nadi, Ba and Sigatoka to curb looting and ensure public safety after heavy rain and flooding over the past four days.

"There is no power in the main town's business district and other areas like Narewa Village where 15 to 20 houses are under water," Nadi mayor Timoci Koroiqica told FijiLive.

The mayor of Ba, Pravin Bala, said the town was under more than a metre (three feet) of water at high tide.

"Police are now monitoring movement in the town area and trying to restrict people from coming into town because one life has been lost already and we don't want that to be repeated," he said.

Dismac officials said more than 2,340 people were sheltering in evacuation centres on Sunday evening.

The Fiji Meteorological Service warned of further heavy rain and strong winds for the northern parts of the country.