SYDNEY, Australia - A powerful earthquake rattled the South Pacific island nation of Papua New Guinea on Tuesday, generating a small tsunami near the epicentre, bringing down power lines and cracking walls, but causing no widespread damage.

A tsunami estimated at under 1 metre was seen in the harbour of Rabaul, a town near the epicenter of the 7.5-magnitude quake, said Chris McKee, assistant director of the Geophysical Observatory in the capital, Port Moresby. There were no reports of flooding, as the tsunami didn't rise beyond the normal level of high tide, McKee said.

The temblor struck at a depth of 42 kilometres, about 130 kilometres south of the town of Kokopo in northeastern Papua New Guinea, the U.S. Geological Survey reported, after issuing varying estimates of the quake's power.

The earthquake brought down power lines in the Rabaul area, knocking out power to residents and to the local Geophysical Observatory office, McKee said. There were a few reports of structural damage in Kokopo, including cracks in some walls, but no reports of injuries, he said.

The Pacific Tsunami Warning Center said that tsunami waves of up to 1 metre were possible within 300 kilometres of the epicentre, but lifted the warning a few hours later. Apart from Rabaul, there were no other reports of unusual wave activity, and any further threat was likely to be minimal, with waves of less than 0.3 metres predicted, McKee said.

Tuesday's quake was centred in the same area as two earthquakes that rocked Papua New Guinea last week. The nation sits on the Ring of Fire, the arc of seismic faults around the Pacific Ocean where earthquakes are common.