The 7.5-magnitude tremor struck 90 kilometres (55 miles) south of Porgera in the Pacific nation’s Enga province early Monday, with two strong aftershocks rattling the rugged region.
Phone lines were largely cut, but the PNG Post Courier newspaper cited Hela provincial administrator William Bando as saying there were casualties.
It reported that at least 13 died in the Southern Highlands capital Mendi while 18 others were believed to have been killed in nearby Kutubu and Bosave.
Some 300 people were injured, it added, and properties damaged, with reports of landslides and sinkholes.
The Papua New Guinea Today website, quoting Catholic priest Pius Hal, said at least 10 died, including four children, in quake-triggered landslides.
A government assessment team was due to fly into the area Tuesday to get a better idea of the impact, with the military mobilised to help restore services and infrastructure, the government’s Chief Secretary Isaac Lupari said in a statement.
“Information will be provided as this is made available from assessment teams in the area,” he added.
Hela governor Philip Undialu, who was in the capital Port Moresby, told The National newspaper there was widespread damage.
“The scale of damage, from information we are getting from the ground, is quite extensive,” he said, adding that there were around 19 landslides between Mendi and the town of Mount Hagen.
“Our police station, courthouse, hospital … even private houses have been ripped apart or sunk into the ground.
“It’s going to be a massive recovery exercise.”
The tremor hit at a depth of 35 kilometres around 3:45 am (1745 GMT Sunday), US seismologists said, with aftershocks of 6.0 and 6.3 magnitude recorded.
Agnes Kep told the Post Courier she was asleep in Mendi when the quake struck.
“We could feel the house and the earth shaking, we wanted to run for the door and out of the house, but it was too late,” she said, fearing that if they went outside “the ground might open up and swallow us”.
The thatched roof on the house she was in collapsed “but we didn’t care, we just clung to each other and waited for the shaking to stop”.
“When we came out we barely recognised everything around us, nothing was familiar to us. The house or tree that was there wasn’t there anymore,” she added.
The region is home to oil and gas production.
ExxonMobil PNG said buildings at its Hides Gas Conditioning Plant were damaged but all its staff were “safe and accounted for”, with non-essential employees to be evacuated.
Australian resources company Oil Search on Monday said its operations in the area were being shut down as a precaution and for damage assessment, and there were no injuries reported among its staff so far.
Earthquakes are common in PNG, which sits on the so-called Pacific Ring of Fire, a hotspot for seismic activity.