Fijian authorities have warned people to prepare as Cyclone Evan lashes the Pacific nation, packing very high winds.
Flights to and from Fiji were cancelled as the category four storm approached from the north.
Thousands of people are in evacuation centres, with storm warnings in effect for the whole nation.
Cyclone Evan hit Samoa last week, killing at least four people and causing widespread flooding.
The latest media release from the Fiji Meteorological Service, at 16:00 local time (03:00 GMT), said the storm was 28km (17 miles) north-west of the tourist centre of Nadi.
Winds close to the centre were estimated at between 170-185 km/h (105-115mph), it said, with storm-force winds extending 90km from the centre.
Early reports suggested that power had been lost in some areas, with reports of flooding and structural damage.
"I cannot stress enough how serious this is. Every Fijian will be affected but we must take preventative steps now," leader Frank Bainimarama said.
Government spokeswoman Sharon Smith-Johns said: "Members of the public are advised to prepare for the worst".
Australia has offered expert personnel and supplies to both Samoa and Fiji.