The Pacific Tsunami Warning Center said there was no tsunami threat from the quake. (Representational)

A strong 6.6-magnitude earthquake struck near the Pacific island nation of Vanuatu Thursday, the US Geological Survey said, but no tsunami warning was issued.

USGS said the quake hit about 178 kilometres (110 miles) northwest of the capital Port Vila at 2:02 am (1502 GMT Wednesday) at a depth of 179 kilometres.

The Pacific Tsunami Warning Center said there was no tsunami threat from the quake.

USGS said there was a low likelihood of casualties and damage.

Vanuatu is part of the "Ring of Fire," a zone of tectonic activity around the Pacific frequently subject to earthquakes and volcanic eruptions.