Fiji lifted emergency restrictions Thursday after the Pacific nation avoided a direct hit from Tropical Cyclone Zena and the storm weakened as it moved offshore.

Authorities had imposed a nationwide curfew as Zena bore down on the main island Viti Levu overnight Wednesday, fearing a repeat of super cyclone Winston, which killed 44 people in February.

But meteorologists said Zena weakened, rather than intensifying, and tracked further south than expected, staying out to sea and leaving the island relatively unscathed.

"After a blissfully uneventful night across Fiji we can give thanks," Suva's Nadraki weather forecasting service said.

"All who planned for the worst and hoped for the best were rewarded for their efforts by having everything turn out okay."

The cyclone was preceded by heavy rain and flash flooding that claimed two lives, but the UN humanitarian agency OCHA said it could have been much worse.

"Viti Levu has been spared a second major disaster in as many months," it said.

"The weather has now dramatically improved in most areas and flood waters are starting to subside."

Roads reopened and international flights resumed, with a police-enforced curfew lifted early Thursday.

But OCHA said the thousands of people still in temporary accommodation after Winston -- the most powerful storm in Fiji's history -- had a "miserable night" in heavy rains.

"Health and hygiene concerns remain including the risk of mosquito and water-borne diseases," it said.

Forecasters said Zena had been downgraded to a category two system and was heading east towards neighbouring Tonga, where authorities warned residents to expect thunderstorms, high winds and heavy swells.