An earthquake of magnitude 7.6 struck off Tonga, the United States Geological Survey said.
The quake struck at 4am NZT, with its epicentre at a distance of 95km west-north-west of Hihifo, Tonga, the USGS said.
It was at a depth of 210km.
The US Tsunami Warning System said there was no tsunami warning after the earthquake.
The quake was followed by a 5.1 magnitude aftershock at 4.30am NZT.
Hihifo is the main village on the island of Niuatoputapu north of the Tonga main island group.
In Samoa, people had evacuated to higher ground following the quake.
A tsunami warning was issued by the Samoa Meteorological Service but later lifted. No other warnings were issued.
The quake was felt in American Samoa. A journalist in Tuālāuta County said the shaking lasted at least a minute or two.