A 6.3-magnitude earthquake has struck off Papua New Guinea but no tsunami alert has been issued and there are no early reports of casualties.

The US Geological Survey said it had hit at about 0915 local time (2315 GMT) and was centred about 29km (18m) east of the Pacific state's city of Lae.

The quake was registered at a depth of 66km (41m).

The island Papua New Guinea shares with Papua is historically prey to volcanic activity, earthquakes and tidal waves.

Officials told AFP news agency that villagers had reported cracks in buildings and a damaged water tank in the Hidden Valley gold-and-silver mine area, near the town of Lae, but no collapsing houses.

"The earthquake was strongly felt, mostly in the Wau and Bulolo areas," Lawrence Anton, a seismologist at the country's Geophysical Observatory in Port Moresby, added.

"We would expect a bit of damage to village houses."