The Pacific Tsunami Warning Centre put the quake at a strength of 7.7
A strong 7.5 magnitude earthquake struck off the coast of Papua New Guinea on Tuesday, the US Geological Survey said, triggering warnings of hazardous tsunami waves.
The shallow quake occurred around 1300 GMT, some 44km northeast of Kokopo on New Britain island, the USGS said.
"It was massive, absolutely massive. Very scary," Megan Martin, the managing director of the Ropopo Plantation resort in Kokopo, told AFP.
"There does not appear to be any damage, but we are out checking."
The Pacific Tsunami Warning Centre put the quake at a strength of 7.7.
"Based on the preliminary earthquake parameters hazardous tsunami waves are possible for coasts located within 1,000km of the earthquake epicentre," the centre said.
In a follow-up alert, it added that waves from 0.3 metres to one metre above the tide level were possible for PNG, while waves of less than 0.3 metres might be expected throughout the region - including Japan, Taiwan, the Philippines and Indonesia.
"Government agencies responsible for threatened coastal areas should take action to inform and instruct any coastal populations at risk in accordance with their own evaluation procedures and the level of threat."
An AFP reporter in Kokopo said electricity went off in the town after the quake struck.
"We won't know until the morning if there is serious damage, but the whole area is experiencing power blackout," he said.
"Aftershocks are still being felt."
Papua New Guinea's rugged highlands region was hit by a 7.5-magnitude quake in February last year that buried homes and triggered landslides, killing at least 125 people.
The scale of that disaster did not become apparent for days due to PNG's poor communications and infrastructure.
There are regular earthquakes in the country, which sits on the so-called Pacific Ring of Fire - a hotspot for seismic activity due to friction between tectonic plates.