International warships bound for New Zealand to celebrate the country's naval history this week have been drafted to help earthquake relief efforts.

Naval ships from the United States, Canada and Australia were bound for Auckland - the northern part of New Zealand's north island to celebrate the 75th anniversary of New Zealand's navy - but they have been diverted to the south island, parts of which have been devastated by a quake measuring 7.8 on the Richter scale.

"It's heartening to see overseas partners so willing to alter their plans and offer their assistance," Defense Minister Gerry Brownlee said.

Brownlee said Wellington had also accepted unspecified aid from the militaries of Japan and Singapore in the aftermath of the quake that killed two people and caused billions of dollars worth of infrastructure damage when it hit early Monday.

The resort town of Kaikura bore the brunt of the seismic shock. On Tuesday, New Zealand military helicopters began airlifting 1,200 holiday makers trapped in the seaside town - and more help is on the way.

The navy ship HMNZS Canterbury is expected to arrive later Wednesday and Brownlee said he was also sending three other New Zealand vessels.

He said the international vessels already on site were Canada's HMC Vancouver, Australia's HMAS Darwin and the US destroyer USS Sampson.

Nuclear free zone

The Sampson is the first US warship to visit New Zealand in 33 years. For decades the Wellington government barred US military vessels from its ports because they are powered by nuclear energy. New Zealand declared itself a nuclear free zone in the early 1980s.

The stand-off was finally resolved last July.

US Secretary of State John Kerry passed through New Zealand on Sunday, and said the Sampson's presence was a historic moment marking "the normalization of our security cooperation."

Massive landslides have blocked roads and rail lines, in some cases cutting off entire communities.

Prime Minister John Key said rescuers are delivering much-needed supplies to the hardest-hit areas before starting a clean-up that is likely to cost billions of dollars.

"It's more water and food, it's more chemical toilets, it's fixing up the road access, getting those tourists out and then ultimately the big clean-up job," he told TVNZ.

But in the chaos that followed the quake he missed a call from US President-elect Donald Trump.

"I didn't see it. It was a crazy time," he said. "Look, he is trying to make contact and that'll happen sometime pretty soon... I'll keep my phone on."

bik/kl (AFP, Reuters)