More than 670 people are assumed to have died in Papua New Guinea's massive landslide, the UN migration agency estimated on Sunday as rescue efforts continued.

Media in the nation had previously estimated Friday's landslide had buried more than 300 people. But more than 48 hours later the International Organisation for Migration (IOM) said the death toll may be more than double that, as the full extent of the destruction is still unclear and continuing dangerous conditions on the ground are hampering aid and rescue efforts.

Only five bodies had been retrieved from the rubble so far.

The agency based its death toll estimates on information provided by officials at Yambali Village in the Enga province, who say more than 150 houses were buried in Friday's landslide, Serhan Aktoprak, the chief of the agency's mission in Papua New Guinea said in an email statement.

"Land is still sliding, rocks are falling, ground soil is cracking due to constant increased pressure and ground water is running thus the area is posing an extreme risk for everyone," Aktoprak said.

More than 250 houses nearby have been abandoned by the inhabitants, who had taken temporary shelter with their relatives and friends, and some 1,250 people have been displaced, the agency said.

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

The IOM said an elementary school, small businesses and stalls, a guesthouse, and a petrol station were also buried.

The UN's Papua New Guinea office said five bodies were retrieved from an area where 50 to 60 homes had been destroyed, and a number of injured reported, including at least 20 women and children.

IOM said the community in this village was relatively young and it's feared that the most fatalities would be children of 15 years or younger.

The geographic remoteness and the tough, hilly terrain is slowing rescue and aid efforts. (Reuters)