SYDNEY: A 6.8-magnitude earthquake struck off the coast of Tonga Saturday in the tectonically active Pacific region, but there was no tsunami threat, seismologists said.

The tremor hit at a depth of 10 kilometres (six miles) some 90 kilometres off the Tonga island of Niuatoputapu, and 230 kilometres southwest of the Samoan capital Apia, the US Geological Survey reported.

The Pacific Tsunami Warning Center said there was no current tsunami threat.

The quake lasted for almost one minute, and caused residents to leave their homes for open spaces across Samoa, according to reports cited by the Samoa Observer news website.

Tonga and Samoa are part of the "Ring of Fire", a zone of tectonic activity around the Pacific that is subject to frequent earthquakes and volcanic eruptions.