The epicentre was reported to be 680km from Port Moresby and monitoring agencies have confirmed that a tsunami was not expected.
The quake occurred at a depth of 48.9km, according to the US Geological Survey.
Little damage was expected from the earthquake, as it was focused in a jungle area with roads and nearby villages.
The island is located on the Pacific Australia tectonic plate within the high seismic activity zone of the so-called "Ring of Fire".
PNG regularly is hit by earthquakes in the order of more than magnitude-7.0.