The epicentre was 35 kilometres (22 miles) deep and located about 300 kilometres (190 miles) east of the New Caledonian archipelago, it said.
Any tsunami waves are expected to be less than 0.3 metres (one foot), the Pacific Tsunami Warning Center said in its latest update.
The waves may reach the Pacific islands of Fiji, Kiribati, Vanuatu and Wallis and Futuna, it said, after earlier issuing a warning for coasts within 300 kilometres (185 miles) of the epicentre.
On Friday, a 7.7-magnitude quake in the same area sent people scrambling for higher ground on several Pacific islands for fear of giant waves. A tsunami warning was lifted hours later.