A powerful magnitude 8.1 earthquake has struck in the ocean off the coast of New Zealand 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.

That is because of the remoteness of where they hit. The largest struck about 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 defence 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 quake could cause tsunami waves of between one and three metres in French Polynesia and waves of up to one metre in Niue, New Caledonia and the Solomon Islands.

The US Geological Survey said the larger quake was centred in the remote Kermadec Islands at a depth of 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 north-eastern coast.

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 13 miles under the ocean about 108 miles north east 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 the city centre.