People in Fiji are being warned the window of opportunity to prepare to be hit by the powerful Cyclone Yasa is closing.

Evacuation centres have opened with the category five storm expected to make landfall tonight.

At least 600,000 people lie in the path of the cyclone which packs winds gusting up to 350km/h.

The Director of the National Disaster Office, Vasiti Soko, said people should either move into evacuation centres or secure their homes and clear loose items in their surroundings.

Soko warned the winds would be destructive

"It's strong enough to uproot trees, it's strong enough to uproot buildings, those that are not well secured, and therefore it can also cause a lot of flying debris."

On its current track, Cyclone Yasa is expected to move between the two main islands of Viti Levu and Vanua Levu tonight.

However, Stephen Meke, a forecaster from Fiji's Meteorological Service, said impacts were already starting to be felt.

"We have reports from the Yasawas that they are getting some damaging gale force winds. Also from Vanua Levu, the other large island of Fiji, as of last night they have reported that they have continuous heavy rain and some damaging gale force winds."

Meke said the winds were starting to pick up over the Western half of Fiji.

As of yesterday, people had started moving into evacuation centres but more were being encouraged to do so.

"Time is limited now as severe Tropical Cyclone Yasa narrows in on Fiji," Meke said.

"We've been telling them [the public] this is one of those tropical cyclones, especially when it comes from the northwest, it brings in all these damaging storm surges as well."

via met.gov.fj

Suva-based correspondent Lice Movono, said government services were moving to help people in vulnerable locations such as the informal settlements where many on Viti Levu live.

"But there are still people going to work, there are still people preparing to go to work today even though the civil service itself has kept their non-essential staff at home," Movono told RNZ's Morning Report.

"In some places where memories of [Cyclone) Winston are still fresh people are moving very quickly, but I think there needs to be a lot more urgency given the scale of the cyclone that's coming for us now."

Communication on disaster preparedness was stronger since the 2016 cyclone, she said, and donor partners and development agencies had a lot of experience in getting aid to the outer islands.

"But given this cyclone, unlike any other, is coming straight for the two major islands where our urban centres are, where our businesses are and most importantly where our government infrastructure is located, it's quite a different picture we're looking at - we're I think quite fearful, if I may say so."

Stephen Meke said the impacts could be similar to the 2016 Cyclone Winston which killed 44 people, flattened villages and caused hundreds of millions of dollars worth of damage.