Suva, March 31 A 7.0-magnitude earthquake jolted 79 km SSE of Pangai, Tonga, at 1:18 local time on Monday, the US Geological Survey said.
The US Tsunami Warning Center issued an alert saying hazardous waves could be possible, but later said there was no longer a tsunami threat, Xinhua news agency reported.
The epicentre, with a depth of 10 km, was initially determined to be at 20.495 degrees south latitude and 174.111 degrees west longitude.
There were no immediate reports of casualties or damage.
The Pacific Tsunami Warning Center issued an alert, warning that hazardous waves could affect coastlines within 300 km (185 miles) of the epicentre.
A local resident told Xinhua that the earthquake was felt strongly in the capital Nuku'alofa, but his house was not damaged at all.
"Hazardous tsunami waves from this earthquake are possible within 300 km (186 miles) of the epicentre along the coasts of Tonga," the US tsunami warning system said.
There were no immediate reports of damage.
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.
The Tourism Ministry published an evacuation map on Facebook for the capital Nuku'alofa.
Pacific island countries such as Fiji, Tonga and Vanuatu lie on the so-called Pacific "Ring of Fire," an arc of earthquake and volcanic zones where continental plates collide, producing frequent seismic activities.
Tonga is a Polynesian nation consisting of 171 islands and has a population of just more than 100,000 people, with the majority residing on the main island, Tongatapu. It is located more than 3,500 km (2,000 miles) east of Australia's coast.
Most islands boast white sandy beaches, coral reefs, and dense tropical rainforests.
The main island, Tongatapu, is surrounded by lagoons and limestone cliffs. It hosts Nuku'alofa, the kingdom's rural capital, along with beach resorts, plantations, and the Ha'amonga 'a Maui, a historic coral stone gateway dating back to the 1200s.
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