Winds gusting up to 150 k/ph (93 m/ph) hit Fiji's main islands of Viti Levu and Vanua Levu, causing floods, blackouts and damage to homes and buildings.
Two people were electrocuted by collapsed power lines and another man died in a house fire, while others were killed by the storm.
Over 450,000 residents in many parts of the country, including the capital Suva, have no power or water. Forecasters warned that flood warnings would remain in force on the Pacific island.
Fiji's authorities recently started restoring power, Radio New Zealand International reported, with water supplies across the country expected to get back to normal by Thursday morning.