The United Nations migration agency on Sunday said some 1250 people had been displaced from the landslide that occurred in Papua New Guinea's Enga province early morning on Friday.
More than 150 houses were buried and around 250 houses nearby have been abandoned by inhabitants.
"The houses are buried under around eight metres of dirt. So there is quite a lot of debris to get through," aid group CARE International PNG country director Justine McMahon told ABC television on Monday.
Villagers search through landslide debris in Yambali, in the Highlands of Papua New Guinea. (AP PHOTO)
McMahon said dangerous conditions and unstable land were hampering rescue efforts. An estimated 4000 people were living near the impacted area, she said.
Residents have rescued a couple, who had been trapped under the rubble, after they heard their cry for help, media reported.
Social media footage posted by villagers and local media teams showed people scaling rocks, with many digging with shovels, sticks and their bare hands to find survivors. Women could be heard weeping in the background in videos.
Emergency crews, including the PNG defence engineering team, were on the ground but heavy equipment required for the rescue had yet to reach the village as the main road remains cut off and the only access was via helicopter.
Neighbour Australia and France, which rules the Pacific island of nearby New Caledonia, have said they stand ready to assist PNG.
There has been no official counts on the deaths though the UN migration agency on Sunday estimated more than 670 people may have died, more than double the initial number of possible fatalities reported by the PNG media.
The UN said only six bodies had been retrieved from the rubble so far.
