The quake was also felt in Malaysia and in Singapore, 430km from the epicentre, where some office buildings were evacuated.
Sergeant Gunawaman, a police spokesman, said no injuries were reported but the damage could be extensive, with at least one collapsed building.
"Everything in my house fell down... a cabinet hit me," said Rahma Nurjana, a Padang resident.
"My neighbour's house collapsed."
The Indonesian archipelago sits on the Pacific Ring of Fire where continental plates meet, causing frequent seismic and volcanic activity.
In December 2004, a massive earthquake struck off Sumatra triggering a devastating tsunami that killed more than 230,000 people, including 131,000 people in the Aceh province alone.
A tsunami off Java island last year killed nearly 5,000.