The populations of Vanuatu and New Caledonia are similar, with just over 280,000 people living in each archipelago.
New Zealand, for its part, quickly announced that its residents would face "no tsunami threat".
"Hazardous tsunami waves from this quake are possible within 1000km of the epicentre along the coasts of Vanuatu and New Caledonia", the Pacific Tsunami Warning Centre said.
New Zealand, which falls within the radius, is not under threat, the Ministry of Civil Defence and Emergency Management declared via Twitter.
The Pacific Tsunami Warning Center confirmed tsunami waves had been observed following the quake.
New Caledonia and Vanuatu ordered coastal evacuations on Wednesday after a powerful undersea natural disaster triggered tsunami warnings in the South Pacific, but appeared to have suffered little damage.
New Zealand authorities quickly rescinded its tsunami warnings after seeing the threats weren't vital to its coast.More news: 'Baller', 'So Special' - Some Fans Praise Arsenal Star For Display Against Vorskla
A massive quake has struck beneath the waters of the South Pacific, and dangerously powerful waves may soon follow.
Authorities said the quake, followed by at least 20 strong aftershocks, was centred about 170 kilometres (100 miles) southeast of New Caledonia's Loyalty Islands at a depth of just 10 kilometres.
Mr Rene said so far there were no reports of a tsunami or damage in the Loyalty islands.
But the centre later reported waves measured by its monitors around the region only reached about 72 centimetres (2.4 feet) on the island of Tanna, Vanuatu.
"The building shook, but there was no damage". High ground, say officials, is anything taller than 39 ft above sea level. "For now, nothing serious has happened".
Residents of New Caledonia, which lies north of New Zealand, received an urgent text message directing them to go to refuges immediately.
Neighbouring island Vanuatu also issued evacuation warnings.
Local journalist Charlie Rene told RNZ the tremor could hardly be felt in the capital Noumea about 300 kilometres from the epicentre.