Many more were missing and feared to have been washed out to sea when Monday's tsunami struck without warning.
Observers say that monitoring buoys and warning sirens installed since the devastating December 2004 Indian Ocean quake and subsequent tsunami did not work due to lack of maintenance.
Monday's 7.7 magnitude temblor struck at 9:42 p.m. local time about 150 miles west of the Sumatran provincial capital of Bengkulu at a depth of less than 13 miles, according to the U.S. Geological Survey.
Seismologist Kerry Sieh of the Earth Observatory of Singapore said Monday's jolt was actually an aftershock of the December 2004 earthquake, and occurred along the same thrust fault that runs parallel to Sumatra's southwestern coast.
He also cautioned that he and other scientists feel with utter confidence that an even larger quake will strike the same region in the future with far more deadly consequences.