A powerful magnitude 7 undersea earthquake struck east of New Caledonia's Loyalty Islands in the South Pacific on Monday, sending small tsunamis towards New Caledonia and neighbouring Vanuatu, where authorities ordered evacuations.

The Pacific Tsunami Warning Center in Hawaii issued a tsunami warning for coastlines within 300 kms (186 mile) of the epicentre, saying wave heights would vary depending on coastlines and that the initial wave may not be the largest.

It said small tsunamis had been detected and forecast waves up one metre (three feet) above the high tide level to hit parts of New Caledonia and smaller waves for Vanuatu.

"We are a little bit scared, we have had an earthquake last night and today it was quite a big one," said Wayan Rigault, communications manager at Hotel Nengone Village on the island of Mare, which is the closest landmass to the epicentre.

Rigault said there was no immediate damage, but guests were on alert for a formal evacuation warning.

Vanuatu's National Disaster Management Office advised people in southern provinces to evacuate coastal areas for higher ground.

New Caledonia's civil security agency said it was still compiling data, and was not planning to evacuate immediately.

Authorities in Australia, New Zealand and Hawaii said there were no tsunami threats to the coastlines of those countries.

Monday's quake, initially reported as magnitude 7.3, struck at a shallow depth of 10 km (six miles) about 82 kms (51 miles) east of New Caledonia, and was the second major tremor in the same area in just over 12 hours and the third in the past month.