The United States Geological Survey has reported the quake was at a depth of 10km and and the US Tsunami Warning Center has issued a tsunami threat warning.
The epicentre of the earthquake was about 178km east-southeast of Kimbe, a town on the north east of the island, which was just north of Australia.
An early prediction from the US National Weather Service NOAA said there was a 1-3m tsunami threat for Papua New Guinea, issued at 9.29am.
Aftershocks have also begun with a 5.3 magnitude quake hitting near the epicentre at 9.39am.
Comment: Just 2 months earlier also in the south of the city: Pit bull put down after attacking, killing woman in Tucson, Arizona