A powerful earthquake with a magnitude of 7.5 struck off Papua New Guinea late Saturday, the US Geological Survey said.

A tsunami warning was issued for Papua and the Solomon Islands by the Hawaii-based Pacific Tsunami Warning Center, but it later cancelled the alert.

The quake struck 75 kilometres (47 miles) southwest of the town of Panguna on Bougainville island at a depth of 30 kilometres just before 11:30 pm (1330 GMT), USGS said.

The seismologists said another 5.6-magnitude quake hit the same area around 20 minutes later at a depth of 69 kilometres.

6.6-quake hits off PNG's Bougainville: USGS
Sydney (AFP) April 19, 2014 - A strong 6.6-magnitude earthquake struck off Papua New Guinea's Bougainville Island Saturday but there was no risk of a widespread tsunami, seismologists said.

The quake, scaled back from an initial reported magnitude of 6.9, hit at 0104 GMT and was centred 59 kilometres (36 miles) southwest of the town of Panguna on Bougainville at a depth of 24 kilometres, the US Geological Survey said.

In its initial estimate the USGS said there was a low likelihood of casualties and damage.

According to the Hawaii-based Pacific Tsunami Warning Center there was no threat of a destructive widespread tsunami based on historical data.

Geoscience Australia measured the quake at magnitude 7.0 and said it was probably felt within a wide radius, with the potential for localised shaking damage.

"Because it's such a large event there's a possibility of damage in that area," seismologist Emma Mathews told AFP.

"But it's nothing out of the ordinary for such an earthquake-prone country."

Mathews said it was the latest in a recent cluster of earthquakes in the Panguna region, with five events recorded in the past week including powerful magnitude 7.6 and 7.5 tremors that triggered a local tsunami alert.

Those jolts were felt locally but there were no reports of significant damage from remote and isolated Bougainville, which sits between the island of New Guinea and the Solomons.

The rumblings sparked panic in the Solomons capital Honiara, reeling from floods earlier this month that claimed at least 21 lives.

"This is quite an active area, an active tectonic area that receives a high frequency of earthquake activity," Mathews said.

Quakes of such magnitude 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.

In October, a 7.1-magnitude quake struck in the same area -- around 65 kilometres west of Panguna.

Last year in February the remote town of Lata in the Solomons was hit by a devastating tsunami after an 8.0-magnitude earthquake. The tsunami left at least 10 people dead, destroyed hundreds of homes and left thousands of people homeless.