A strong 6.9-magnitude earthquake struck off Papua New Guinea on Monday, officials said, but no Pacific-wide tsunami warning was issued with little damage expected due to the remote location.

The tremor was estimated at a depth of 35 kilometres (22 miles) on New Britain island, 418 kilometres northeast of the capital Port Moresby, the United States Geological Survey said.

The Hawaii-based Pacific Tsunami Warning Center ruled out a widespread tsunami.

"Based on all available data, there is no tsunami threat from this earthquake," it said.

Australian seismologists estimated the quake at 6.8-magnitude and said damage was highly unlikely with few inhabitants in the area.

"Luckily it is a very, very remote part of New Britain," Geoscience Australia duty seismologist Dan Jaksa told AFP.

"It's highly unlikely there is any damage given the remoteness."

New Britain, the largest island of the Bismarck Archipelago, is east of mainland New Guinea and has a population of around 500,000 people.

It lies on the 4,000-kilometre Pacific-Australia plate, which forms part of the "Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates.