No damage or casualties were immediately reported but images showed a tower of ash soaring into the sky above Mount Ibu, located on the remote island of Halmahera in North Maluku province.
The huge grey and black ash column was "seen in thick intensity and leaning towards the west", said Indonesia's Center for Volcanology and Geological Hazard Mitigation in a statement.
It called on locals and tourists not to go within five kilometres of Ibu's crater.
"If ash fall occurs, residents carrying out outdoor activities are suggested to wear nose, mouth, and eye protections," it said.
Ibu also erupted on Monday, spewing another ash tower five kilometres above its peak.
Last week authorities raised Ibu's alert status to the second-highest level.
Mount Ibu is one of Indonesia's most active volcanos, erupting more than 21,000 times last year.
More than 700,000 people lived on Halmahera island as of 2022, according to official figures.
Indonesia, a vast archipelago nation, experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire".
Last month, Mount Ruang in North Sulawesi province erupted more than half a dozen times, forcing thousands of residents of nearby islands to evacuate.
It remains at the highest alert level.
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