Cyclone Yasa intensifies to category 4 with winds of up 200km/h

A severe cyclone brewing in the South Pacific has rapidly intensified, with winds gusting to 200km/h.

Forecasters say the huge storm could reach category-five strength and are warning Fiji to prepare for a major weather event.

Cyclone Yasa developing between Vanuatu and Fiji has been bumped up from category two to a severe category four cyclone, forecaster WeatherWatch said.

The storm has strengthened incredibly fast with winds between 160km/h to 200km/h around the centre, and some gusts expected to surge higher, it said.

"All eyes should be on this storm as it churns just offshore from Vanuatu and is likely going to have a decent impact on parts of Fiji," the forecaster said.

There is a moderate risk of Yasa reaching New Zealand but only a low risk of it still being classed as a "storm" by then, WeatherWatch said.

"It may also bring some wind, rain and dangerous seas around Vanuatu for a time from the east."

There are two cyclones brewing in the Pacific, Yasa and Zazu. Photo / WeatherWatch

The cyclone is set to hit Fiji on Thursday evening or Friday morning.

By that time, it could have swelled to the highest storm category - five, the weather forecaster said.

"Those in Fiji should immediately begin preparing for a major weather event."

Earlier on Tuesday, a second tropical cyclone, Zazu, was identified in the South Pacific.

Cyclone Zazu is tracking at sea between Tonga and the Cook Islands and does not pose a threat to New Zealand, WeatherWatch said.

As of Tuesday evening, Cyclone Zazu was category two and had sustained gale-force winds around its centre.