A magnitude 6.6 earthquake has struck off the coast of Papua New Guinea's New Britain island, but there were no immediate reports of damage, according to the US Geological Survey.

The Pacific Tsunami Warning Center in Hawaii said on Friday that there was no tsunami threat from the quake. The earthquake, which hit a depth of 69km, was initially reported at 6.9 magnitude before being revised lower.

The undersea quake struck in a narrow strait between New Britain's south coast and the north coast of Papua New Guinea's main island, the US Geological Survey said.

"It would have been very widely felt," seismologist Emma Mathews from Geoscience Australia, was quoted as saying by the Australian newspaper.

Mathews said while the threshold for a local tsunami was any quake within a depth of 100km, the Pacific Tsunami Warning Centre said that based on all the available data there was no threat of a destructive wave.

Ring of Fire

Geoscience Australia said the tremor could have been felt by people up to 836km away from its epicentre off the sparsely populated west coast of the island of New Britain, while damage could have been caused within a 67km radius.

There were no immediate reports of damage.

Earthquakes are common in Papua New Guinea, which sits on the so-called Pacific Ring of Fire, a hotspot for seismic activity due to friction between tectonic plates.

In April a powerful 7.1-magnitude tremor struck off Papua New Guinea off the town of Panguna on the remote and volcanic Bougainville island.

It was followed by a 6.7-magnitude quake a little further from the town.

In 2013 the neighbouring Solomons Island were hit by a devastating tsunami after an 8.0-magnitude earthquake rattled the region. That tsunami left at least 10 people dead, destroyed hundreds of homes and left thousands of people homeless.