The shallow quake hit 90 kilometres (56 miles) southeast of the village of Pangai, with warnings also extending to the island nation of Niue.

"Tsunami waves reaching 0.3 to 1 meters above the tide level are possible for some coasts of Niue... and Tonga," The US tsunami warning system said.

It had earlier warned that "hazardous tsunami waves from this earthquake are possible within 300 kilometres of the epicentre along the coasts of Tonga".

The Tonga national disaster agency issued a warning to residents to stay away from beaches and shorelines.

"People living on the low lying coast areas please move to higher grounds or further in land," the Tonga National Disaster Risk Management Office wrote on Facebook.

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.