The quake struck at 7:03 a.m. at a depth of 20 kilometres, according to the United States Geological Service.
The epicentre was located 163 kilometres east of Raoul Island -- the largest of the Kermadec Islands -- and 1,185 kilometres northeast of Auckland, New Zealand.
The Pacific Tsunami Warning Centre (PTWC) issued a local tsunami warning for New Zealand and Tonga.
Sea level readings showed the quake did generate a small tsunami. Peak wave heights of 2.7 feet were recorded on Raoul Island, the PTWC said.
The New Zealand Civil Defence Office ordered people to stay off the beaches and out of the water while the warning was in effect.
The Kermadec Islands are uninhabited except for a weather station and a hostel for visiting scientists.
With files from the Canadian Press.