A fourth earthquake has struck off Papua New Guinea, the US Geological Survey says.

The magnitude 6.1 earthquake follows a powerful magnitude of 7.5 in the area on Saturday night, which sparked a tsunami warning for PNG and the Solomon Islands.

The Hawaii-based Pacific Tsunami Warning Center later cancelled the alert.

The latest earthquake struck 96km southwest of the town of Panguna on Bougainville at a depth of 18 kilometres at 10.30am (AEST) on Sunday, USGS said.

A 5.6-magnitude quake hit the same area on Saturday night at a depth of 69 kilometres, after a 6.6-magnitude tremor on Saturday morning.

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 February last year the remote town of Lata in the Solomons was hit by a devastating tsunami after an 8.0-magnitude earthquake.

It left at least 10 people dead and thousands homeless.

- APNZ