The quake had a depth of approximately 50 kilometres (31 miles), and struck outside Kimbe, in the West New Britain region, at about 1:13 am (1513 GMT Wednesday), the USGS said.

There were no immediate reports of damage or injuries, and no tsunami warning was issued.

Earthquakes are common in Papua New Guinea, which sits on top of the seismic "Ring of Fire" -- an arc of intense tectonic activity that stretches through Southeast Asia and across the Pacific basin.

Although they seldom cause widespread damage in the sparsely populated jungle highlands, they can trigger destructive landslides.

At least seven people were killed in April last year when a 7.0-magnitude quake hit a jungle-clad area in the country's interior.

About 180 homes were destroyed in the heavily rainforested Karawari area, near the quake's epicentre.

Many of the island nation's nine million citizens live outside major towns and cities, where the difficult terrain and lack of sealed roads can seriously hamstring search-and-rescue efforts.