A strong 6.0-magnitude earthquake struck off Indonesia's Sumatra island early this morning , the US Geological Survey said.
The quake hit at 07:01am (0531 IST) and was centred 224 kilometres south-southwest of the town of Sibolga at a depth of 35 kilometres under the sea, the USGS said.
Local meteorologists said the quake measured 5.6 on the Richter scale and struck at a depth of 51 kilometres.
It was felt in the town of Padang in west Sumatra, but there were no immediate reports of casualties or damage and no tsunami warning was issued.
The Indonesian archipelago sits on the Pacific Ring of Fire where continental plates meet, causing frequent seismic and volcanic activity.
A 7.7-magnitude earthquake in July 2006 off the south coast of the main island of Java killed more than 600 people.
A series of dozens of powerful tremors hit Indonesia following 7.6 and 7.5 magnitude quakes that struck off the West Papua provincial capital Manokwari earlier this month.
Around 14,000 people flooded into camps on high ground in the aftermath of those quakes fearing deadly waves after authorities issued and then withdrew a tsunami alert.
The tremors re-awakened bitter memories of similar deadly quakes that hit Manokwari in 2002, as well as the Asian tsunami that killed 168,000 people in Indonesia's Aceh province and Nias island in 2004.