Jakarta - A strong earthquake struck off the western coast of the Indonesian island of Sumatra late Saturday. There were no immediate reports of injury and structural damage, seismologists said.

The quake, measuring 6.7 on the Richter scale, jolted Sumatra's Bengkulu province at 11:01 pm (1601 GMT). Its epicentre lay about 142 kilometres south-west, the National Meteorology and Geophysics Agency (BMG) said, about 23 kilometres beneath the seabed in the Indian Ocean.

The US Geological Survey put the quake's magnitude at 6.8 on the Richter scale.

Officials said there were no immediate reports of casualties or damage following the quake, which was followed by a 6.3-magnitude aftershock about 10 minutes later.

It was the latest of series of earthquakes to jolt Indonesia in recent days.

On Monday, a powerful 7.7-magnitude undersea earthquake struck off Indonesia's North Sulawesi province, killing at least seven people, injuring more than 150 others and damaging hundreds of homes.

Indonesia is prone to seismic upheaval due to its location on the Pacific's so-called "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin.

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 around 
500,000 homeless. (dpa)