A 7.5-magnitude earthquake struck off the coast of Papua New Guinea Monday, sending startled residents fleeing from their homes, but a tsunami threat passed with no immediate reports of major damage.

The quake hit at a depth of 33 kilometres (20 miles), some 55 kilometres from the nearest city of Kokopo on New Britain island and 787 kilometres from the capital Port Moresby, the United States Geological Survey said.

The Pacific Tsunami Warning Centre initially cautioned that "hazardous" tsunami waves could hit some coastal areas in PNG. It later updated its advice to say the threat had passed.

It noted a reading of waves 0.03 metres (0.1 feet) above the tide level at Tarekukure Wharf, some 450 kilometres from the epicentre. Information from coastal areas closer to where the quake struck was sketchy.

Mathew Moihoi from Papua New Guinea's Geological Observatory said officials were still unable to make contact with more remote areas to determine whether there had been any sea level changes.

"We've not been able to receive such information from the people as to whether a tsunami has been observed or not," he said.

Leonie Fakal, a housekeeper at the Seaview Beach Resort in Kokopo, said all the staff and their two guests ran outside when the quake hit.

"Everybody was a bit afraid. There was a lot of shaking and some things fell down in the hotel," she told AFP soon after the quake.

"Everyone ran outside but there was not much damage."

John Amos, a reception clerk at the Kokopo Beach Bungalow Resort, added that the quake produced a powerful jolt but there was no damage.

"It was the biggest earthquake we have experienced so far," he said.

"We had one big one and then some smaller wobbles. But we seem to be quite ok. There is no damage and it's quiet here now."

He added that staff were "keeping an eye on the beach" for any unusual ocean activity.

The initial quake was followed by a smaller 5.7-magnitude aftershock in the same area.

- Quakes common in PNG -

Geoscience Australia seismologist Jonathan Bathgate said there was a possibility of a local tsunami but based on the magnitude of the quake it was likely to be on the lower end of the scale.

"It would have been quite widely felt, certainly within 100 kilometres," he told AFP of the quake.

"It's probably not going to be damaging. Although people would have felt strong shaking... there's probably not going to be a lot of widely spread damage."

The nearest town of Kokopo, the capital of East New Britain, has a population of around 20,000. It started to grow after nearby Rabaul was flattened by volcanic eruptions in 1994.

Chris McKee from the Geological Survey in Papua New Guinea earlier said he had spoken with people on neighbouring New Ireland and that they did not even feel the quake.

He added that constructions in the area were mostly wooden and "seem to be able to soak up the shakes quite well".

Earthquakes are common in PNG, which sits on the so-called Pacific Ring of Fire, a hotspot for seismic activity due to friction between tectonic plates.

The last big tremor off the Pacific nation's coast was a 6.8-magnitude quake that struck Bougainville island in December.

In 2013 the neighbouring Solomon Islands were hit by a devastating tsunami after an 8.0-magnitude earthquake rattled the region. That tsunami left at least 10 people dead, destroyed hundreds of homes and left thousands of people homeless.