The second quake registered a magnitude of 5.7 and came 30 minutes later northwest of the city of Padang.
The third quake hit North Sumatra province at 8:24 am with a magnitude of 5.5.
Four of the deaths occured in the town of Muarasipongi, in the western part of North Sumatra province, according to an official with the Padang meteorology office.
Mosques, churches and houses were also reported damaged in the town.
The quakes also triggered a landslide that blocked a key road leading to the region and impaired efforts to reach victims.
Besides the three quakes, dozens of aftershocks have shaken the area officials said.
Sumatra lies just east of one of the world’s most active fault lines and is hit by frequent earthquakes.