The quake struck at a depth of 36 kilometres (22 miles) at 0709 GMT, 60 kilometres northeast of Isangel in Vanuatu and 324 kilometres northeast of Tadine in the French Pacific territory of New Caledonia, according to USGS.

There was no threat of a widespread tsunami, the Pacific Tsunami Warning Centre said.

"However earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within a hundred kilometres of the earthquake epicentre," it said.

The area lies on the so-called "Pacific Ring of Fire", a zone of frequent seismic activity caused by friction between shifting tectonic plates.