Three strong earthquakes have been recorded south of Samoa by the U.S Geological Survey just hours after a magnitude-7.5 had Papua New Guinea on tsunami watch.

A map showing the location of a cluster of magnitude-6.8 earthquakes near Samoa

Three earthquakes struck about 165km south of Apia, the first at 9:18pm New Zealand time before two more struck about 9:48pm.

All were recorded as being magnitude 6.8, with the first two at a depth of 10km and the third at a depth of 55km.