The earthquake followed two very strong 7.3 and 7.4 magnitude tremors, prompting thousands to seek higher ground.
A powerful magnitude 8.1 earthquake struck in the ocean off the coast of New Zealand on Friday, prompting thousands of people to evacuate and triggering tsunami warnings across the South Pacific.
The quake was the largest in a series of tremors that struck the region over several hours, including two earlier quakes that registered magnitude 7.4 and magnitude 7.3.
While the quakes triggered warning systems and caused traffic jams and some chaos in New Zealand as people scrambled to get to higher ground, they did not appear to pose a widespread threat to lives or major infrastructure because of the remoteness of where they hit.
The largest struck about 1,000 kilometres (620 miles) off the coast of New Zealand.
One of the earlier quakes hit much closer to New Zealand and awoke many people during the night as they felt a long, rumbling shaking.
"Hope everyone is ok out there," New Zealand prime minister Jacinda Ardern wrote on Facebook.
After the largest quake, civil defense authorities in New Zealand told people in certain areas on the East Coast of the North Island that they should move immediately to higher ground and not stay in their homes. They said a damaging tsunami was possible.
The US Tsunami Warning System also cautioned that the larger earthquake could cause tsunami waves of between 1 to 3 metres (3 to 10 feet) in French Polynesia and waves of up to 1 metre (3 feet) in Niue, New Caledonia and the Solomon Islands.
The Pacific Tsunami Warning Center said tsunamis could later strike Hawaii.
The US Geological Survey said the larger quake was centred in the remote Kermadec Islands at a depth of 19 kilometres (12 miles).
Officials in New Zealand had hours earlier issued a tsunami warning for coastal areas after the first of the smaller earthquakes struck off its northeastern coast at about 3 am on Friday. There were no immediate reports of serious damage or casualties, and the warning was lifted just before the larger quake struck.
The US Geological Survey said the first quake was centred at a depth of 21 kilometres (13 miles) under the ocean about 174 kilometres (108 miles) northeast of the city of Gisborne.
It was widely felt in New Zealand, and residents in the major cities of Auckland, Wellington and Christchurch reported being shaken awake.
In 2011, a magnitude 6.3 quake hit the city of Christchurch, killing 185 people and destroying much of its downtown.