A magnitude 6.7 earthquake struck northeastern Papua New Guinea on Saturday, the United States Geological Survey said, with no immediate reports of damage.

The strong quake had a depth of 53 kilometres (33 miles) and hit at around 7:30 pm (0830 GMT) with the epicentre about 56 kilometres southeast of the coastal town of Madang, the USGS said.

An aftershock of equal magnitude hit off the coast of Madang minutes later, the USGS said.

Earthquakes are common in Papua New Guinea, but rarely cause widespread damage.

Outside major towns and cities, most areas are sparsely populated, and what buildings there are tend to be made of wood.

But some quakes are more destructive.

In April, at least seven people were killed when a 7.0 magnitude quake hit a jungle-clad area on the Pacific island nation.

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