Mount Ruang, located in the Sangihe Islands arc in North Sulawesi province, has been increasingly active in recent weeks. Authorities on Tuesday raised the alert level to the highest possible after new eruptions, warning of potential pyroclastic flows, deadly ash surges and the possibility of tsunami.
The eruption also caused a power outage on neighboring Tagulandang island and forced the closure of Sam Ratulangi International Airport in Manado, disrupting air travel in the region, officials said.
"A total of around 6,500 people have been evacuated from five districts," Feri Ariyanto, a search and rescue official in Manado city, told dpa.
Abdul Muhari, the spokesman for the National Disaster Management Agency, said 12,000 residents who live within a 7-kilometer radius around the volcano would have to be evacuated.
The Indonesian archipelago sits on the seismically active "Ring of Fire" and is no stranger to volcanic eruptions and earthquakes.