WELLINGTON, May 11 (AFP) - A 7.6-magnitude earthquake rattled the Pacific island nation of Tonga in the early hours of Thursday (May 11) but there were no reports of injuries or damage.

The quake struck at 4.02pm GMT about 100km off Tonga's remote volcanic island of Niuatoputapu at a depth of 210km, the US Geological Survey said.

There was no tsunami risk, it said.

"We had calls early in the morning from people who felt it, but there have been no reports of damage," said Gary Vite, chief meteorologist at Tonga Meteorological Services near the capital Nuku'alofa.

The quake was also felt some 360km from the epicentre in the Samoan capital Apia.

A spokesman for the Samoa Meteorological Service said "strong vibrations" shook the office near Apia but there had been no reports of damage.

Tonga and Samoa sit on the Pacific "Ring of Fire", where tectonic plates often shift, frequently experiencing seismic activity.