Two separate blasts lasting between 10 and 15 minutes occurred in quick succession, according to the regional Volcanological and Geological Disaster Mitigation Center.
Since awakening with a comparable eruption last August, Mount Marapi has produced frequent tremors and other signs of volcanic activity.
Marapi, not to be confused with the better-known Mount Merapi on Java, is Sumatra's most active volcano.
It has produced more than 50 eruptions since records began at the end of the 18th century.
No lava flows have ever been seen escaping its summit craters.