A strong magnitude 8.2 earthquake, 566 kilometres deep, has struck in the Pacific Ocean close to the island nations of Tonga and Fiji.

A Civil Defence and Emergency Management spokesman said there was no threat to New Zealand.

National weather service US Pacific Tsunami Warning Centre said small tsunami waves have been observed.

"While no hazard is expected for any coastline, but please be observant and exercise normal caution."

Kiwi Cara Michael who was in Fiji with her family said "buildings were swaying, made you feel a bit seasick almost but it stopped after about half a minute".

Despite that everyone was "pretty relaxed here as you'd expect", she told the Herald.

One person in Lautoka, the second biggest city in Fiji said they felt the whole building shake, making them think it was flexible.

No casualties are expected based on initial readings and there has been no reports on damages.

The quake hit at a depth of 347.7 miles (559.57 kilometres) and was initially reported as magnitude 8.2.

The epicentre was 167 miles (270 kilometres) east of Levuka on Fiji's Ovalau Island and 275 miles (443 kilometres) west of Neiafu in Tonga, a town with a population of around 6,000 people.

More to come.