Australia's department of foreign affairs warned its citizens in New Caledonia to seek safety.
A shallow and powerful 7.5-magnitude earthquake struck off New Caledonia Wednesday prompting a tsunami alert and evacuations on the Pacific island, authorities said.
There have been no reports of injuries or serious damage.
Authorities said the quake, followed by at least 20 strong aftershocks, was centred about 170 kilometres southeast of New Caledonia's Loyalty Islands at a depth of just 10 kilometres.
Residents of New Caledonia, which lies north of New Zealand, received an urgent text message directing them to go to refuges immediately.
"We activated the alert sirens... along the east coast and all the Loyalty Islands," Eric Backes, director of the islands' civil defence authority, told local radio.
Island residents said the initial quake shook the walls of buildings and in places turned the sea foamy.
Tsunami waves were recorded moving out from the epicentre, prompting people to flee to high ground.
Basile Citre, a municipal official on the Loyalty Island of Mare, said the situation there was so far under control.
"I was in a meeting at the town hall and we felt a small tremor then a bigger one," he told AFP.
"The building shook, but there was no damage. When the sirens sounded, the population headed for higher ground for safety. For now, nothing serious has happened."
Waves measured by quake monitors around the region only reached about 72cm on the island of Tanna, Vanuatu.
Geoscience Australia seismologists monitoring the event said a tide gauge on Mare Island, the second-largest of the Loyalty Islands, had registered a signal for a 43-centimetre wave height.
Multiple aftershocks of up to magnitude 6.6 hit the area in the hours following the initial quake, according to the US Geological Survey.
"Based on that, we can say that this earthquake has generated a tsunami, but we don't know the impact and how far it could go onshore," seismologist Spiro Spiliopoulos told AFP.
Tsunami sirens were not immediately activated in Vanuatu - or in Fiji where they tested the tsunami warning system earlier this week and some coastal communities could be brushed by tsunami waves.
A spokesman for the Vanuatu geohazards observatory said the sparsely populated island of Tanna was expected to be most affected but no evacuations had been ordered.
"There are no sirens on Tanna but the people on the island are familiar with these situations and they will have taken precautions and gone to higher ground," he told AFP.
New Caledonia, with a population of 269,000 people, is a French Pacific territory.
Its citizens last month rejected independence in a referendum, though the vote revealed lower-then-expected support for remaining part of France.
The island is home to a quarter of the world's known supplies of nickel - a vital electronics component - and is a foothold for France in the Pacific, with French troops stationed on the island.