The shallow quake, at a depth of 10 kilometers (six miles), triggered a tsunami warning which was later downgraded by the US Pacific Tsunami Warning Centre.

"Based on all available data the tsunami threat from this earthquake has now passed," the centre said, adding that "no tsunami was observed" at the nearest monitoring site.

The earthquake struck at 6:04 am local time (2004 GMT) and was centred about 194 kilometres (120 miles) southeast of the nearest major town Kimbe.

Marolyn Simbiken, a receptionist at Kimbe's Liamo Reef Resort, said so far she had not seen any damage.

"We did feel the earthquake here," she told AFP.

"But there's not big damage. Nothing was damaged here and there was no evacuation."

Walindi Plantation Resort worker Barbara Aibilo she felt a "slight shake".

Several smaller quakes, with preliminary magnitudes ranging from 4.9 to 5.3, struck afterwards near the same patch of sea, according to the USGS.

Earthquakes are common in Papua New Guinea, which sits on top of the seismic "Ring of Fire" -- an arc of intense tectonic activity that stretches through Southeast Asia and across the Pacific basin.

Although they seldom cause widespread damage in sparsely populated areas, they can trigger destructive landslides.