An offshore earthquake measured at 7.0-magnitude earthquake has shaken Papua New Guinea, according to the US Geological Survey.

The epicentre of Tuesday's quake was 137 kilometres north of the coastal city of Lae at a depth of 202 kilometres.

Papua New Guinea's Geophysical Observatory said the quake was felt as far as the capital Port Moresby on the country's southern coast.

There were no immediate reports of damages or injuries from the earthquake, and no tsunami warning was issued by the Pacific Tsunami Warning Center.

Papua New Guinea is in the geologically active "Ring of Fire" Pacific region and suffers many earthquakes.

But it often avoids major damage and casualties because many people live in light and flexible housing.

However, a 7.0-magnitude quake off the north coast in 1998 led to more than 2,000 deaths and a tsunami that smashed into isolated villages.