Whakatane (New Zealand), Dec 13 (AFP) A team of elite New Zealand soldiers landed on a volatile volcanic island Friday on a perilous mission to retrieve bodies left when an eruption hit visiting tour groups earlier this week, police said.

AFP witnessed two military helicopters set off from Whakatane airport at first light for White Island, the offshore volcano where an eruption last Monday is believed to have killed at least 16 people.

At the same time, police took grieving families out near the volcano on a boat to perform a Maori blessing and locals chanted karakia, or prayers, on the shore as the island smouldered in the distance.

Authorities say eight bodies remain on the volcano, which sits semi-submerged 50 kilometres (30 miles) out to sea.

After coming under pressure from distraught families a recovery mission was approved despite a 50-60 per cent chance of another blast from the volcano in the next day or so.

As the eight-strong military team wearing protective clothes and gas masks attempt to extract the bodies, vulcanologists will monitor live feeds from the mountain, ready to abort the operation if signs point to another eruption.

As they began the mission, White Island was at "Alert level 2" - the highest before an eruption.

"Of course I'm worried, I would be inhuman if I did not worry," deputy police commissioner Mike Clement said outlining the plan late Thursday, adding "we have a job to do".

Six of the eight bodies were located on the island with data from drone flights and help from helicopter pilots who were near the volcano immediately after the eruption.

The plan is to immediately recover the six bodies and search for the other two, then transport them to military frigate HMNZS Wellington anchored off the coast, Clement said.

The operation is expected to take several hours.

"People are putting themselves on the front-line to do the right thing... our thoughts and our prayers and our love will be with them," Clement said.

The bodies on the island are thought to include New Zealand tour guide Hayden Marshall-Inman.

His brother Mark Inman has epitomised families' frustrations with stalled recovery efforts, putting the five-day delay down to "red tape, bureaucracy" and failed leadership, while offering to go to the island himself.

A visibly anguished Prime Minister Jacinda Ardern on Thursday expressed empathy with the families, but insisted "everyone is desperate to get those victims back".

After days of caution, police approved the mission rather than lose the chance to returning identifiable remains to grieving families.

On White Island poisonous gases are still billowing from the volcanic vent and the island is blanketed in a thick layer of acidic ash.

GeoNet vulcanologist Nico Fournier said the dangers facing recovery teams if an eruption occurred included magma, superheated steam, ash and cannonball-like rocks thrown from the caldera at supersonic speed.

While officials weighed how to recover the bodies, another 29 people -- mostly tourists who had been on a day trip to see the natural wonder -- are still being treated in hospitals across New Zealand and Australia, many in a critical condition suffering severe burns.

The survivors' injuries were so severe New Zealand doctors initially estimated they would need to import 1.2 million square centimetres (185,000 square inches) of skin for grafts -- although that was likely to be revised down as victims were moved overseas to ease the strain on hospitals.

A total of 47 day-trippers and guides were on the island during the eruption, with police saying they were in two groups, one of which was closer to the volcanic vent and worst hit.

Those caught by the eruption hailed from Australia, the United States, Britain, China, Germany, Malaysia and New Zealand.

Australian Prime Minister Scott Morrison said one Australian was confirmed dead and a further 10 were missing and presumed to have perished.

Canberra has sent three military aircraft with specialist medical crews to repatriate some of the survivors, with at least 12 Australians expected to be flown to burns units in the country.

Malaysia previously said one of its citizens had died in the tragedy, but a foreign ministry official told AFP late Thursday the victim had in fact survived and was in a critical condition.

"The victim will be flown to Australia for further treatment," the official said. British, German and US officials said their citizens were among those hurt.

A coronial process has begun to identify the eight confirmed dead but police said it could "take some time". (AFP)

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