Fiji's Vanua Levu pummelled by TC Yasa overnight

Cyclone Yasa has been downgraded to a category 4 storm but is still packing winds of at least 195km/hr with gusts of 275km/hr.

Tonga has now issued a cyclone warning as forecasts show it tracking close to the islands over the weekend.

Many houses in Fiji's Vanua Levu have been destroyed, some families sheltered under beds and tables in their houses and others in cane plantations, as Cyclone Yasa wreaked havoc in many parts of the Northern Division, Fiji Village reports.

Buildings and crops were destroyed on Vanua Levu, Fiji's second largest island, and there's been widespread flooding and landslides.

There are widespread power outages, and phones are down, after winds of 240km/h - with gusts as high as as 345km/h.

Yasa is heading south through the Southern Lau Island group.

People in Fiji's northern division described Cyclone Yasa as the scariest experiences of their lives.

"It's a nightmare," said Banuve Lasaqa Lusi, a resident of Labasa, the main town on Vanua Levu. "The thunderous sound of the wind and what is flying around is what's frightening.

She said the sound of the wind was deafening, and power and some communication had been cut out from the town; "I've never seen one like this... it's heartbreaking

In the province of Bua some people had to flee as their houses disintegrated in the wind. Video from Bua shows sheets of torrential rain pelting the ground, and roofs being lifted by the sheer force of the gale.