A 6.9 magnitude earthquake has struck off the Pacific island nation of Vanuatu.

The US Geological Survey said the quake struck at 08:23 GMT, 420km (260 miles) north-west of the capital, Port Vila.

The Pacific Tsunami Warning Centre said the threat of tsunami waves had now mostly passed.

The USGS said the quake was fairly shallow - at a depth of about 35km (21 miles) - but no damage had been reported so far.

The quake, originally measured at 7.2, struck in the north of Vanuatu off Espiritu Santo.

Quakes are fairly common in the region. Two similar sized tremors last October and December caused no damage.

Vanuatu has a population of about 270,000, with some 44,000 living in Port Vila.