The quake prompted warnings for the Pacific Islands region which was downgraded just hours later by the US Geological Survey. The earthquake struck about 50km east of Taron, at a depth of 103km.
The Pacific Tsunami Warning Centre warned hazardous waves were possible in the Pacific but said later in the early hours of the morning that the tsunami threat had ended, combined reports from Radio New Zealand and Reuters said.
The Pacific Tsunami Warning Centre had said waves reaching 1-3m above the tide level were possible in coastal areas of Papua New Guinea for several hours.
The Geophysical Observatory in Port Moresby said a tsunami smaller than 1m hit the coast of the island of New Ireland shortly after the earthquake.
Waves of less than 0.3m above the tide level were forecast for other areas of the Pacific, including Indonesia, Solomon Islands, Nauru and Vanuatu.
Waves of less than a metre in height were observed at Tarekukure Wharf in Solomon Islands.
Many residents in the northern parts of the autonomous region of Bougainville sought higher ground amid warnings that tsunami waves were possible.
A nurse at the Buka General Hospital in Bougainville, Tracey Anunfi, said the patients at the hospital's four wards were taken to higher ground, and stayed there all night.
"All of us, including the hospital and everyone down at the town area, we all managed to move up. There's higher ground, it's at Hahela, we managed to get there and all of us went into the cathedral there."
Anunfi said nurses brought medication to the church for the patients, who had since returned to the hospital.
Papua New Guinea is situated on the Ring of Fire, the arc of seismic faults around the Pacific Ocean where earthquakes are common. It's a vast area where about 90 per cent of the world's earthquakes occur, according to the USGS.
The ring, which actually is shaped more like a horseshoe, includes more than 400 underwater volcanoes and stretches 400 kilometres from New Zealand, past Japan, across the Bering Strait and down to the tip of South America.