Tsunami waves have been detected after an undersea earthquake struck 82km east of New Caledonia's Loyalty Islands.
The magnitude 7.0 quake struck east of New Caledonia's Loyalty Islands, prompting a tsunami warning for coastlines within 300km of the epicentre.
The Pacific Tsunami Warning Centre says waves as high as 1 metre above the high-tide mark are forecast to hit New Caledonia and smaller waves are expected in Vanuatu.
It says the actual size of the waves will vary depending on the coastline, with barrier reefs reducing wave height, and warned that the initial wave may not be the largest.
The quake, initially reported as magnitude 7.3, is the second major tremor in the same area in less than 24 hours and the third in the past month.
Monday's quake struck at 9.43am local time at a shallow depth of 10 km, east of the remote Loyalty Islands, the United States Geological Survey says.
The Pacific Tsunami Warning Centre said hazardous tsunami waves were possible along the coastlines of New Caledonia and Vanuatu.
"Government agencies responsible for threatened coastal areas should take action to inform and instruct any coastal populations populations at risk," the PTWC said in an alert.
New Zealand officials say there is no tsunami threat.
New Caledonia is about 2300km north of New Zealand.
NZ Civil Defence says there is no tsunami threat.
"Based on current information, the initial assessment is that the earthquake is unlikely to have caused a tsunami that will pose a threat to New Zealand," it tweeted.