The Mount Ibu volcano on Indonesia’s Halmahera island erupted on Thursday, sending grey ash 2,500 metres above its peak.
There were no reports of casualties but locals and visitors have been advised to stay away from a two kilometre exclusion zone, said Axl Roeroe, an official with the Ibu Volcano Observatory.
He said those working outside should use protective masks.
Halmahera is part of the Moluccas Islands.
Indonesia sits on the Pacific Ring of Fire, an area known for seismic upheavals, and has about 128 active volcanoes.