Cyclone Daman has swept past Fiji's second-largest island, Vanua Levu, veering away from populated areas where forecasters had warned of major damage.
But the category four storm lashed the small northerly island of Cikobia with winds of up to 250km/h (155mph).
Officials said brief radio contact with the stricken island indicated the storm had caused "injuries and maybe deaths".
"We've got to be thankful that it missed the two larger islands of Fiji," said forecaster Alipate Waqaicelua.
Fiji's Disaster Management Office said it had lost contact with Cikobia, home to as many as 100 people, after the storm struck it at about 0300 Fijian time Saturday (1500 Friday GMT).
"It seems islanders fled when the storm blew their homes away, so it will take some time to gauge a more accurate picture of the extent of the damage," Joji Satakala, an official at the office told a local broadcaster.
Mr Waqaicelua said the storm was now heading out towards open water between Fiji and Tonga.
"While the cyclone is weakening slowly, it's still packing a very strong punch," he said.
Warnings of flash-floods in low-lying areas and high-tide flooding remained in place early on Saturday morning local time.
Earlier, the Disaster Management Office had warned people living in low-lying areas in the Lau, Lomaiviti and Vanua Levu island groups to move to shelters or higher ground as the storm surged in from the north-west.
Serious damage from flash floods, wind gusts and up to 25cm ( 10 inches) of rain had been expected.
Cyclone Daman had been upgraded to a category four storm on Friday, and forecasters had feared it would sweep away the flimsy houses that many of Fiji's islanders live in.
Although the majority of Fiji's tourist resorts are located on and around the country's largest island, Viti Levu, south of the storm's path, some tourists were reported to have been evacuated from the Yasawa Islands chain.
The Australian government warned citizens visiting Fiji to find out where cyclone shelters were and contact families at home.
"In some areas, adequate shelter from a severe cyclone may not be available to all who may choose to stay. You should review and follow hotel or cruise ship evacuation plans," it said in a travel advisory. ( BBC )