A strong 6.0-magnitude earthquake struck Papua New Guinea on Wednesday morning, the US Geological Survey said, but there were no immediate reports of damage or casualties on the ground.

The quake hit at 9:28 am (2328 GMT Tuesday) with an epicentre 117 kilometres (73 miles) south-southwest of Rabaul, which sits at the northern tip of the island of New Britain, at a depth of 47 kilometres, the USGS said.

Residents of Rabaul felt the tremor but there were no reports of damage, according to PNG's earthquake authority.

"We heard from our colleagues at the Rabaul monitoring station that the earthquake was felt, I would say, moderately to strongly," said authority spokesman Lawrence Anton.

"Water sloshed out of water tanks and gave a lot of people a fright, but there was no damage at this stage reported," he told AFP.

The Pacific Tsunami Warning Centre had indicated there was "no major concerns of a tsunami," he said.

The quake came just one week after a major 7.9-magnitude tremor rattled the South Pacific nation of Tonga, sending people in low-lying areas of Fiji fleeing for higher ground after a tsunami warning.

Papua New Guinea was last hit by a major earthquake last August, when a 6.3-magnitude quake shook Lae, its second-largest city, without significant damage.

The impoverished country is home to many active volcanoes and sits on the Pacific "Ring of Fire" where several tectonic plates collide. The region is frequently rocked by earthquakes.