A 7.8-magnitude quake hits central New Zealand, killing at least two people and prompting a tsunami warning.

A powerful magnitude 7.8-magnitude earthquake has rocked New Zealand, prompting a tsunami warning and knocking out power and phone services in many parts of the country.

Prime Minister John Key said at least two people were killed in the powerful temblor.

Officials warned all people along the east coast of the country to get to higher ground as the first waves began to roll in.

The US Geological Survey said the shallow quake hit 90km from the South Island city of Christchurch, which was devastated five years ago by a 6.3 tremor.

That quake killed 185 people in one of New Zealand’s deadliest disasters.

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Monday’s earthquake, initially put at 7.4 but later upgraded, struck at 12:02am local time (1102 GMT on Sunday).

It was only 10km deep and felt throughout most of the country.

It was followed by a series of strong aftershocks and there were reports of damaged buildings in the small rural township of Cheviot near the epicentre.

“It was massive and really long,” Tamsin Edensor, a mother of two in Christchurch, told AFP news agency.

“We were asleep and woken to the house shaking, it kept going and going and felt like it was going to build up.”

A handout map showing the quake’s location 90km from Christchurch [USGS/EPA]

Civil Defence organisation, which is in charge of New Zealand’s emergency management, said it was too early to assess the damage or whether there had been any injuries or deaths.

“The whole house rolled like a serpent and some things smashed, the power went out,” a woman who gave her name as Elizabeth told Radio New Zealand from her home in Takaka, near the top of South Island.

The ambulance service said it did not receive any reports of quake-related injuries.

Civil defence warned people along the country’s east coast to move to higher ground amid fears of a tsunami.

“The first wave activity may not be the most significant,” it said in a bulletin, adding tsunami activity would continue for several hours.

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Anna Kaiser, a seismologist at GNS Science, said a tidal signal or surge of up to one metre had been recorded in the North Canterbury region of the South Island.

“That’s reasonably significant so people should take this seriously,” she told Radio New Zealand.

The Pacific Tsunami Warning Centre, however, said that based on available data “a destructive Pacific-wide tsunami is not expected”.

Chris Hill, a fire officer in Cheviot, said officials had gone door to door evacuating residents.

“Everyone seems okay here,” he told Radio New Zealand. “There’s a lot of debris in houses, but at this stage it doesn’t look like anything too bad has happened.”

In a brief message the Prime Minister John Key tweeted: “I hope everyone is safe after the earthquake tonight.”

In September, a strong 7.1-magnitude earthquake struck the east coast of New Zealand, generating a small tsunami, but no significant damage or injuries were reported.

New Zealand is on the boundary of the Australian and Pacific tectonic plates, which form part of the so-called “Ring of Fire”, and experiences up to 15,000 quakes a year.