The Pacific country of Tonga has been battered by a powerful cyclone, causing extensive damage across the main island.

With destructive winds of 230 kilometres per hour, category four Cyclone Gita ripped roofs from houses, brought down trees and caused widespread flooding.

“It was a terrifying night,” Grahame Kenner from Tonga’s National Emergency Management Office (NEMO) said.

“I have been doing disaster responses for 30 years and I think it’s the scariest night that I’ve had. It was horrific.

“We’re on the third floor of one of the safest buildings in Nuku’alofa and the building was shaking and getting pounded by debris from missing roofs.”

There are so far no confirmed reports of deaths.

But emergency authorities said about 70 per cent of the population had been affected and food and water would be a significant problem.

“Wind was blowing and we heard roofing torn and flying over, it was quite scary,” NEMO director Leveni Aho said.

Hundreds of military personnel were clearing roads and disaster teams were already assessing the damage.

“We are sending teams to the field now, but it’s still raining and still fairly windy,” Mr Aho said.

“So it’s going to be some time before we get a quick overview of the damages to the nation.”

Weather experts say Gita shows no signs of abating as the storm continues to head towards Fiji’s southern Lau islands.

It is expected intensify to a category five cyclone as it passes over the Ono-i-Lau group of islands.