The quake near Papua New Guinea sparked tsunami warnings in the immediate area.

A powerful earthquake off the coast of Papua New Guinea generated a small tsunami and knocked out power in parts of the Pacific island nation. A tsunami warning was also issued for New Zealand early on Sunday.

The magnitude-7.9 quake struck 46km east of Taron on Saturday (Sunday NZT), the US Geological Survey said. The quake was deep, at 103km. Deeper earthquakes tend to cause less damage than shallow ones.

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The USGS initially said the quake's magnitude was 8.0, but later downgraded the strength.

The Pacific Tsunami Warning Centre said there was a threat of a tsunami in Papua New Guinea and nearby areas. It said tsunami waves reaching 1-3m high were possible along the coasts of Papua New Guinea, while waves in other areas, including the Solomon Islands, would likely be less than 0.3m high.

A tsunami measuring less than 1m hit the coast of the island of New Ireland shortly after the earthquake, said Felix Taranu, seismologist with the Geophysical Observatory in the capital, Port Moresby. There were no immediate reports of damage from the tsunami or the quake, though officials were still working to contact people on the island, he said.

The quake knocked items off shelves and caused a blackout in the town of Kokopo in northeastern Papua New Guinea, Taranu said. But there were no reports of widespread damage in the town.

Shortly after the quake, New Zealand's Ministry of Civil Defence & Emergency Management (MCDEM) issued a tsunami warning for all coastal areas, including the Chatham Islands. However at 1.20am on Sunday, that was cancelled.

AUCKLAND: NO EVACUATION is required following the recent earthquake in Papua New Guinea. — Auckland CDEM (@AucklandCDEM) December 17, 2016

Many residents in the northern parts of the autonomous region of Bougainville sought higher ground amid warnings that tsunami waves were possible.

"The town residents have vacated the whole place; those in the villages live higher up, so they're ok, it's just those near the coast," local resident Christabel Biasu told Reuters by phone.

Quakes are common in Papua New Guinea, which sits on the Pacific's "Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates. There were no immediate reports of damage or casualties after Saturday's major tremor.

A nurse at Buka General Hospital in Bougainville said the quake was so strong it felt like the building she was sleeping in would topple. She said patients were being moved a few kilometres to higher ground.

"We have about 16 beds," she told Reuters by phone, declining to give her name. "Most of them are already a suburb up."

The small Pacific nation of Nauru, where one of Australia's offshore immigration detention centres is located, had a tsunami warning in place, according to the official government Twitter account.