TONGA - A 7.9 magnitude quake about 209km south-east of Tonga triggered a tsunami warning in the South Pacific, but it was withdrawn just over an hour and a half later.

The quake hit just after 6am local time and was caused by the eruption of an undersea volcano that sent huge amounts of black smoke and debris into the air.

There were no immediate indications of any damage or casualties on Tonga's main island, Tongan police said in the capital, Nuku'alofa.

In Fiji, about 750 kilometres west of Tonga, authorities warned people in coastal areas to move to higher ground while schools along the coast were closed and government workers sent home.

Many heeded the warning to evacuate to higher ground, but police complained others in the capital Suva gathered at sea walls looking for signs of an approaching tsunami.

US monitors advised that some coastal areas of Hawaii could see a rise in sea level and strong currents lasting up to several hours but said no destructive impact was expected.

Several earthquakes have been felt in Tonga recently.

An undersea earthquake off Sumatra in December 2004 set off a tsunami that killed more than 220,000 people around the Indian Ocean.

In the South Pacific, at least 52 people were killed by a tsunami in the Solomon Islands in April 2007 after an 8.0 magnitude earthquake.