Disaster officials in Fiji are set to deploy aerial surveillance to assess the damage left in Cyclone Winston's wake, amid fears entire villages were flattened by the category five storm.

Torrential rain, wind gusts of up to 325 km/h and waves up to 12 metres high battered the South Pacific nation on Saturday evening in what is thought to be the strongest severe tropical cyclone to ever hit the Southern Hemisphere.

At least five people have been killed and a nationwide curfew remains in place, as authorities begin the monumental task of assessing the extent of the damage and restoring power to parts of the country, which takes in more than 100 inhabited islands.

Prime Minister Frank Bainimarama​ confirmed the death toll, according to a report from the Fiji Broadcasting Corporation.