A strong earthquake of magnitude 6.4 struck Vanuatu's Erromango island in the Pacific Ocean on Thursday, the US Geological Survey said.

It said the quake struck the centre of the island, Vanuatu's fourth largest, at 2009 GMT on Wednesday and was fairly deep at 124.4 miles (200 km), which would have dampened its effect.

Erromango has a population of just under 2,000 people.

The Vanuatu archipelago, east of Australia in the Pacific Ocean, is in the so-called Ring of Fire and is prone to earthquakes.