The quake was detected at a depth of 37 kilometres (23 miles), the US Geological Service said.
Tsunami waves of one-to-three metres (six-to-nine feet) above tide are possible along some coastal areas of Vanuatu, the Honolulu-based Pacific Tsunami Warning Center said.
It also warned of possible smaller tsunami waves of 0.3-1.0 metres in New Caledonia, Fiji, Kiribati and New Zealand.
A hotel receptionist in the New Caledonia capital Noumea told AFP she felt no shaking from the tremor.
A travel agent on the island of Ile des Pins on the eastern edge of the New Caledonia archipelago said she had not felt the tremor or heard any evacuation warning.
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Home/World News/Earthquake Of Magnitude 7.7 Hits Near New Caledonia, Triggers Tsunami Warning