The quake, which was initially reported at 6.9 magnitude before being revised lower, hit at a depth of 65 kilometres (40 miles) in the New Britain region.
"It would have been very widely felt," said seismologist Emma Mathews from Geoscience Australia, which put the quake's reading at 6.6 magnitude and a depth of 69 kilometres. Mathews said while the threshold for a local tsunami was any quake within a depth of 100 kilometres, the Pacific Tsunami Warning Centre said that based on all the available data there was no threat of a destructive wave.
Papua New Guinea is a hotspot for seismic activity
Geoscience Australia said the tremor could have been felt by people up to 836 kilometres away from its epicentre off the sparsely populated west coast of the island of New Britain, while damage could have been caused within a 67 kilometre 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 which 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.