The National disaster centre in Tonga says emergency services are on full alert following an earthquake measuring 7.8 on the Richter scale.
The US geological survey says the quake, which hit just off the coast of Tonga over two hours ago, was also felt in Niue.
Leveni Aho of the National disaster centre in Tonga says a team has been sent out to find the exact location of the quake.
"we are trying to do out best at this time - it's early - we just want to get people to - the main concern is if there a tsunami or anything generated out of that."
The US monitoring centre says the epicentre was 155 kilometres south of Neiafu island and 160 kilometres north-east of Nuku'Alofa, the main island.