People in central Papua New Guinea remain on edge with more than 20 powerful aftershocks rattling the region since Monday's magnitude-7.5 earthquake.
- Aftershocks as powerful as magnitude-6.3
- Soldiers head to affected areas to assess damage
- Authorities say widespread damage expected
Geoscience Australia said the aftershocks had ranged from magnitude-5 to 6.3.
Monday's earthquake struck in the Southern Highlands province in the early hours of the morning, causing damage to buildings and landslides.
There are fears already-damaged buildings in towns like Mendi, the capital of Southern Highlands province which is home to more than 50,000 people, may not survive continuing aftershocks.
The director of PNG's National Disaster Centre, Martin Mose, said communication networks were down and that was making it hard to assess the impact of the quake.
"We would have expected widespread damage," he told the ABC's Pacific Beat program.
"There have been unconfirmed reports coming through of a number of deaths … and of course widespread damage."
The Government said it was sending response teams including defence personnel to the affected areas.
"The Papua New Guinea Defence Force has also been mobilised to assist with the assessment and the delivery of assistance to affected people as well as the restoration of services and infrastructure," Isaac Lupari, the chief secretary to the Government, said in a statement.
Airports and hospitals were among the infrastructure and buildings believed to have been damaged.
"This earthquake … how can I describe it. It's just something else, something I've never experienced," said Philemon Kambu, a bank officer in Mendi.
"In the place I'm from, Pangia in the far south, houses have collapsed."
ExxonMobil, Oil Search halt production
ExxonMobil said it had shut its Hides gas conditioning plant in Hela province and that it believed administration buildings, living quarters and a mess hall had been damaged.
It also said it had suspended flights into the nearby Komo airfield until the runway could be surveyed.
"Due to the damage to the Hides camp quarters and continuing aftershocks, ExxonMobil PNG is putting plans in place to evacuate non-essential staff," the company said in an emailed statement.
PNG oil and gas explorer Oil Search said in a statement it had also shut production in the affected area.
Earthquakes are common in Papua New Guinea, which sits on the Pacific's "Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates.
"This is the Papuan fold-and-thrust belt, so it's a typical movement of faults in that region, but it's big," said Chris McKee, acting director of the Geohazards Management Division in Port Moresby.
Part of PNG's northern coast was devastated in 1998 by a tsunami, generated by a magnitude-7.0 quake, which killed about 2,200 people.