Desperate villagers are digging through rubble to find survivors and retrieve bodies as Papua New Guinea continues to grapple with a landslide that is estimated to have killed at least 670 people.

The collapse of a mountain side early Friday morning during heavy rain wiped out a bustling village in Enga province, with the damage extending for close to a kilometre, observers report.

Less than a dozen bodies have been recovered so far with efforts hindered by rubble 10m (32ft) deep in some places and a lack of adequate equipment.

Local media reported one couple being pulled alive from the rubble as their home, on the edge of affected area, had escaped being wholly buried.

They were saved after rescue workers heard them call out from where they were trapped under layers of rock, the local NBC channel reported.

Emergency personnel deployed to the region are prioritising the evacuation of people from the area where conditions remain precarious, aid officials have told the BBC.

"We've decided to stay out for now to allow the authorities time to properly assess the situation to conduct the rescue and recovery operations," said Justine McMahon, the country co-ordinator of Care Australia, one of the humanitarian aid agencies on the ground.

"The ground is also quite unstable at the moment and it's at risk of triggering further landslide," Ms McMahon said on Monday.

Australia is one of Papua New Guinea's closest neighbours and has long offered it security and aid support.

Earlier, an official for the UN's migration agency in the country had described to the BBC the rescue difficulties.

Serhan Aktoprak from the International Organization for Migration said there were a number of challenges facing teams trying to recover bodies, including reluctance by some grieving relatives to let heavy machinery near their loved ones.

Instead, he said, "People are using digging sticks, spades, large agricultural forks to remove the bodies buried under the soil".

Debris from the landslide, which includes large boulders, trees and displaced soil, is up to 10m (32ft) deep in some areas.

More than 150 houses have been buried, and about 1,250 people have been displaced.

Crews at the scene also say rescue efforts are being hindered by major damage to the sole road leading to the town. The landslide has damaged a length of about 200m (650ft), Ms McMahon said.

Initial reports had put the death toll in the low hundreds but this jumped on Sunday after a UN revision, taking into account updated population numbers.

Locals have noted how the village in recent years had attracted people from other areas who had been displaced by tribal violence in the region.

The Mount Mungalo landslide occurred in the highlands of Enga, in the north of the island nation.