CHRISTCHURCH, New Zealand (AFP) – A powerful 7.8 magnitude earthquake rocked New Zealand early Monday, damaging buildings and triggering a tsunami which saw people in coastal areas fleeing to higher ground.

The ministry of civil defence, responsible for emergency management in New Zealand, described the tsunami as “an event of life-threatening or national significance”.

The shallow tremor was centreed some 90 kilometres (57 miles) north of the South Island city of Christchurch and was felt throughout the country.

Although no injuries were reported, there were reports of widespread damage, with electricity and phone services cut in many areas.

Monday’s quake, struck at 12:02 am (1102 GMT Sunday) and was 23 kilometres deep, the US Geological Survey said after revising its initial estimate which had rated the tremor slightly weaker but much shallower.

It ignited painful memories for residents in Christchurch which was devastated five years ago by a 6.3 tremor which killed 185 people in one of New Zealand’s deadliest disasters.

“It was massive and really long,” Tamsin Edensor, a mother of two in Christchurch, told AFP, describing the powerful quake as the biggest since the deadly 2011 tremor.

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

The main tremor 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.

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

The ambulance service said it did not receive any reports of quake-related injuries however people took to social media to report damage with goods tipped from shelves and shattered glass littering streets.

“Family friends in Cheviot say some houses are gone,” one person tweeted.

Marie Black, a local councillor who lives about 50 kilometres north of Christchurch, told the New Zealand Herald there were reports of damage to buildings in the North Canterbury region.

“It was a significant shake, I have felt several aftershocks and it is very unnerving,” she said.

The ministry of civil defence, which urged people in eastern coastal areas to move to higher ground said “a destructive tsunami is possible.

“The first wave may not be the largest. Waves may continue for several hours,” it said.

Simon Morton, a radio presenter in the capital city Wellington, said he had evacuated his house after noticing the tide dropping away. Other people had joined him in going to higher ground.

Anna Kaiser, a seismologist with the GNS Science, the government’s earthquake monitoring service, said the quakes were close to the coast and there had been tidal movement up to one metre (three feet) in the South Island town of Kaikoura.

“It’s reasonably significant, so people should take this seriously,” she said.

However, the Pacific Tsunami Warning Center said that based on available data “a destructive Pacific-wide tsunami is not expected.”

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 tremors a year.