A 6.0-magnitude undersea earthquake struck off the western coast of Indonesia's Sumatra island on Saturday, but there were no immediate reports of injury or damage, seismologists said.

The quake struck at 4:21 pm (0921 GMT) at a depth of 28 kilometres, about 72 kilometres south-west of Bintuhan on Bengkulu province, Indonesia's National Meteorological and Geophysics Agency (BMG) said.

The agency said there were no immediate reports of injury and structural damage from the quake, the latest earthquake to jolt Indonesia in recent weeks.

Indonesia, the world's largest archipelago, sits on the Pacific "Ring of Fire," the edge of a tectonic plate prone to seismic upheaval.

A major earthquake and subsequent tsunami struck in December 2004, leaving more than 170,000 people dead or missing in Indonesia's Aceh province and half a million people homeless.