The Mount Ibuvolcano 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 2-kilometre exclusion zone, said Axl Roeroe, an official with the Ibu Volcano Observatory.
Those working outside should use protective masks, he said.
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.
