The magnitude-7.7 earthquake was felt at 12.57pm AEST on May 19 near Loyalty Islands and New Caledonia in the South Pacific. Geoscience Australia said the quake hit at a depth of 31 kilometres.

"While evacuations are not necessary for Marine Threat areas, people in these areas are advised to get out of the water and move away from the immediate water's edge," the Bureau of Meteorology (BOM) said.

BOM said a 22-centimetre tsunami wave was observed near New Caledonia after the earthquake.

Warnings may also be issued to Fiji, Vanuatu and New Zealand.

The situation is being "closely monitored" by the Joint Australian Tsunami Warning Centre who will advise those in the path of the tsunami.

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There is no land threat to the Australian mainland or Australian territories, BOM said.

The warning centre said tsunamis can "generate dangerous rips, waves and strong currents that pose a risk to surfers, swimmers, people in small boats and anyone else in the water".

"There may be some localised flooding onto the immediate foreshore."

The first may not be the largest and there will be many waves, it warned.