The death toll from the Fiji super-cyclone hit 42 on Wednesday, officials said, with fears it will rise further as relief teams reach isolated communities.

"42 Fijians now confirmed dead -- disaster officials continue to deploy team to help those affected across Fiji," government spokesman Dan Gavidi tweeted.

The acting head of the Red Cross's Pacific office Ahmad Sami said more fatalities were coming to light as data came in from remote communities.

"The numbers will continue to change as we have better access to information and establish communications," he told AFP.

Severe tropical cyclone Winston lashed the Pacific nation overnight Saturday, packing wind gusts of 325 kilometres (202 miles) per hour and leaving a trail of destruction.

While humanitarian aid is pouring into the main island Viti Levu, some of the worst-hit villages were on remote islands that relief workers have not yet been able to access.

Prime Minister Voreqe Bainimarama on Tuesday acknowledged the problem and asked for patience from affected communities.

"We realise the desperate position that you are in, how traumatic this is for you and your families... but as prime minister, I want you to know that we will not rest until we have reached you."

Former prime minister Laisenia Qarase said he held grave fears for his home island Vanua Balavu, which had not yet been heard from.

Suva-based Qarase said aerial photographs showed there were "probably a thousand houses destroyed" on the island.

"I'm 75-years old and the damage I've seen, the extent of the damage, this must be the worst thing in living memory for Fiji," he told Radio New Zealand.