A 7.0-magnitude earthquake hit the Pacific nation of Vanuatu early Friday, the United States Geological Survey said, with a tsunami warning issued.

The quake, which occurred at a depth of 10 kilometres (six miles) was originally measured at 7.3-magnitude by the National Tsunami Warning Center (NTWC).

"Hazardous tsunami waves from this earthquake are possible within 300 km of the epicentre along the coast of Vanuatu," the NTWC said.