Mount Gamkonora's alert was raised to the highest level, meaning a major eruption could occur within days or weeks, said Saut Simatupang, who is monitoring activities of the volcano on Halmahera island.
Seismic activity at the 5,364-foot mountain increased sharply Monday and two major eruptions were recorded early Tuesday, shooting debris 9,842-feet into the air, he said.
There have been no reports of damage or casualties, Simatupang said, with some 8,400 villagers evacuated to safer areas in the last 24 hours and northward winds blowing smoke away from residential areas.
Halmahera, the main island in North Maluku province, is about 1,500 miles northeast of Jakarta.
Indonesia has more active volcanoes than any other nation because of its location on the Pacific "Ring of Fire" — a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.