The quake struck in the ocean about 45 kilometers east of Papua New Guinea's New Ireland island.
According to CNN, citing the US Geological Survey, the quake struck in the ocean about 45 kilometers east of Papua New Guinea's New Ireland island, also known as Latangai, at about 8:51 p.m. (5:51 a.m. ET).
The PTWC said hazardous tsunamis are possible though about midnight local time along some coasts of that country, as well as the Solomon Islands, Pohnpei, Chuuk, Indonesia, Nauru, Kosrae and Vanuatu.
According to the USGS, Papua New Guinea is along the RING of Fire, a zone of seismic activity and volcanoes around the edges of the Pacific Ocean. It's a vast area where about 90% of the world's earthquakes occur.
The ring, which actually is shaped more like a horseshoe, includes more than 400 underwater volcanoes and stretches 25,000 miles from New Zealand, past Japan, across the Bering Strait and down to the tip of South America, CNN reports.