PORT MORESBY - A strong 6.5-magnitude earthquake struck off the coast of Papua New Guinea Tuesday but there was no immediate tsunami warning, seismologists said.

The US Geological Survey said the quake struck at 8:28 am (6:28 local time), 126 kilometres west of Arawa at a depth of 74 kilometres.

Papua New Guinea sits on the Pacific "Ring of Fire," where continental plates meet. The region is frequently struck by earthquakes.