Downed power lines and flooding are hampering relief efforts in Fiji after one of the most powerful storms recorded in the southern hemisphere tore through the Pacific island nation, flattening remote villages and killing at least five people.

Harsh winds and torrential rains tore up homes and cut power, water and communications links across the nation of about 900,000 people, although Suva, the capital, escaped the brunt after the storm changed direction at the last minute.

Prime Minister Frank Bainimarama confirmed the death toll and declared a 30-day state of emergency, with schools ordered to shut and a nationwide curfew extended until Monday morning.