An earthquake with a magnitude of 7.7 jolted southeast of the Loyalty Islands on Wednesday with a depth of 10 km, the U.S. Geological Survey said. A tsunami alert has been issued.

"Hazardous tsunami waves from this earthquake are possible within the next three hours," the National Weather Service (NWS) Pacific Tsunami Warning Center said.

The quake struck at just after midnight on Thursday local time (1320 GMT) about 415 kilometers east of Vao in New Caledonia, according to the USGS.

The magnitude of the quake was previously measured at 7.9 and 7.5 by the USGS but was revised to 7.7.

There's no immediate report on damage and casualties.

(With input from AFP)