A powerful 6.9-magnitude earthquake struck off Vanuatu Sunday, but a tsunami threat passed with no immediate reports of major damage along the coasts of the Pacific archipelago.

The quake, initially reported as 7.2 magnitude, struck at a depth of 35 kilometres (22 miles), 81 kilometres north-northwest of the town of Port Olry on Espiritu Santo island in Vanuatu at 0823 GMT, the United States Geological Survey said.

It was 407 kilometres from the capital Port Vila. The USGS said there was a ‘low likelihood of casualties and damage’.

The Pacific Tsunami Warning Centre initially cautioned that ‘hazardous tsunami waves’ were possible along the coasts of Vanuatu, but later updated its advice to say the threat had ‘mostly passed’.

Jonathan Bathgate, senior seismologist at government agency Geoscience Australia, said that while Port Olry residents were likely to have felt ‘very intense shaking’, ‘the likelihood is relatively low in terms of serious damage’.

‘I haven't had confirmation of anything (tsunami) impacting the northern coast of that (Espiritu Santo) island at this stage, so that's probably a good sign,’ Bathgate told AFP.

He added that Port Vila residents would have ‘felt a shake but it probably wouldn't be damaging at that distance’.

‘Earthquakes such as this occur quite often in the area, so Vanuatu experiences these earthquakes of similar magnitudes probably fairly regularly,’ Bathgate said.

Vanuatu is part of the ‘Ring of Fire’, a zone of tectonic activity around the Pacific that is subject to frequent earthquakes and volcanic eruptions.