Papua New Guinea sent troops and rescue workers after a powerful earthquake struck the Pacific nation's mountainous interior yesterday and damaged a gas plant and other buildings.
Authorities warned of aftershocks and landslides. There was no official information on fatalities or injuries in the rugged region but one unconfirmed report of deaths.
Assessment teams were heading to affected areas near the 7.5-magnitude quake's epicentre, which the US Geological Survey said was some 90 kilometres (55 miles) south of Porgera in Enga province.
"It is advisable to stay out of multi-storey buildings, to be aware of the potential of landslides, and to be prepared to move to open ground in the event that an aftershock is felt," the chief secretary to the government, Isaac Lupari, said in a statement.
The tremor hit at a depth of 35 kilometres around 3:45 am (1745 GMT Sunday), US seismologists said, adding that there was no tsunami threat.
A 6.0-magnitude aftershock was recorded by the USGS at 4:26pm nearby.
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.