An earthquake measuring 6.1 struck in the Bismarck Sea off the northern coast of Papua New Guinea on Thursday, but residents on the mainland said there were initial no signs a change in sea level.

The quake, which was 10 km (6.2 miles) deep, was centred 675 km (420 miles) north of Papua New Guinea's capital, Port Moresby, said the US Geological Survey (USGS) said on its Web site.

Residents in the towns of Madang and Wewak on Papua New Guinea's north coast said they had not felt the quake -- which hit at 10:40 a.m. (0040 GMT) -- and that there had been no change in sea levels.

'We have not felt anything and we have not seen any change in the sea,' the receptionist at the Windjammer Beach Hotel in Wewak told Reuters by telephone.

In July 1998, two undersea quakes measuring 7.0 in the Bismarck Sea created three tsunamis that killed at least 2,100 people near the town of Aitape on Papua New Guinea's north coast.

In April an undersea earthquake off neighbouring Solomon Islands created a tsunami which destroyed villages, killing 28 people, and leaving thousands of people homeless.

Papua New Guinea and the neighbouring Solomon Islands lie on the so-called Pacific 'Ring of Fire' where volcanic activity and earthquakes are common. - Reuters