Several Twitter users reported that they felt the tremors in Singapore.
According to local media reports, the quake struck at a depth of about 36 kilometres at a distance of about 73 km west of Bengkulu.
There are no immediate reports of damage or tsunami warning.
The Disaster Management Centre (DMC) warns that all coastal communities in Sri Lanka to be on alert due to a strong 6.4-magnitude quake that hit off the Indonesian island of Sumatra this morning.
An quake measuring 6.6 Richter scale jolted Bengkulu province in western parts of Indonesia on Sunday, Muhammad Tizam, official in charge of meteorology and geophysics agency told Xinhua by phone.
Some residents also posted on twitter, wondering whether the tremors were a result of an natural disaster in the region.