Local authorities confirmed fatalities after Mount Lewotobi Laki Laki erupted just after midnight on Monday, spilling hot ash onto a nearby village in the East Nusa Tenggara province.
The Disaster Management Agency had lowered the death toll from earlier reports nine people had died.
A 7-kilometre radius around the mountain was cleared as hot ash was spewed around 2000 metres into the air.
Hadi Wijaya, spokesperson for the Centre of Volcanology and Geological Hazard Mitigation, said wild weather and power outages followed the eruption.
“After the eruption, there was power outage and then it was raining and big lightning which caused panic among residents,” he told Reuters.
The extent of the fatalities and damage is still being assessed.
Local media reported some people had been buried in collapsed homes.
Mount Lewotobi Laki Laki last erupted in January.