The quake took place at 21:19 GMT on Monday, around 33 kilometers (20.5 miles) to the north-west of the town of Bulolo. The epicenter was located at a depth of 126.9 kilometers.
No immediate statement on any damage or casualties was made.
The USGS-linked Pacific Tsunami Warning Center said there is no tsunami threat after the quake, according to Reuters.
Papua New Guinea lies on the so-called Pacific Ring of Fire — an area in the Pacific Ocean extremely prone to earthquakes and volcanic eruptions. About 90 percent of all global seismic activity occurs in this region.