The shallow quake hit 79 kilometres (49 miles) south-southeast of the village of Pangai at 1219 GMT on Sunday.
The US tsunami warning system initially said "hazardous tsunami waves from this earthquake are possible within 300 kilometres of the epicentre along the coasts of Tonga".
It subsequently revised the assessment, saying "the tsunami threat from this earthquake has now passed", but authorities in Tonga issued further warnings.
The Tonga Meteorological Services told residents in the risk area to evacuate inland to high ground, three-storey solid buildings or tsunami evacuation sites.
"Mariners out at sea are advised to move to deep water away from reefs or coasts and remain there until it is safe," it said on Facebook, before later cancelling the advisory.
The tourism ministry published an evacuation map on Facebook for the capital Nuku'alofa.
Earthquakes are common in Tonga, a low-lying archipelago home to around 100,000 people that straddles the seismic Ring of Fire.
The Ring of Fire is an arc of intense tectonic activity that stretches through Southeast Asia and across the Pacific basin.
Related Links
Bringing Order To A World Of Disasters
When the Earth Quakes
A world of storm and tempest
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
