The US Geological Survey said the quake occurred at a depth of 10 kilometres (6 miles), about 163 kilometres east-northeast of Kandrian, New Britain and some 576 kilometres from the capital Port Moresby.
Geoscience Australia, which also measured the tremor at 6.3-magnitude, said the quake was close to the coastline.
"People living in that local area would have gotten a fairly strong shake," seismologist David Jepsen told AFP, adding that some vulnerable structures could have been damaged by the tremor.
"I don`t think there would be a (local) tsunami," he added.
Jepsen said quakes of such magnitude were common in the New Britain region of Papua New Guinea, which sits on the so-called "Pacific Ring of Fire", a hotspot for seismic activity due to friction between tectonic plates.
A 6.7-magnitude jolt hit the country on Friday but there were no reports of damage in the impoverished Pacific island state.
A giant tsunami in 1998, caused by an undersea earthquake or a landslide, killed more than 2,000 people near Aitape, on the country`s northwest coast.
AFP/H-RN
Editor: Jafar M Sidik
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