SYDNEY (AFP) - A 6.4-magnitude earthquake hit in waters off the Pacific island nation of Tonga on Monday (Dec 24), the US Geological Survey said, but no tsunami warning was issued.

The quake struck at a moderate depth of 100km with the epicentre some 85km north of the Tongan capital Nuku'alofa.

There were no immediate reports of damage.

The Pacific Tsunami Warning Centre said there was no tsunami threat.

Baea Filimoehala from the reception at the Emerald Hotel in Nuku'alofa told AFP there was no damage in the capital, describing the quake as a "small one".