Mount Ili Lewotolok has been erupting off and on since October 2017. The Volcanology and Geological Hazard Mitigation Centre raised the volcano's alert level to the second-highest level on Sunday after sensors picked up increasing activity.
The 5423m mountain is one of three erupting in Indonesia, along with Merapi on Java island and Sinabung on Sumatra island.
They are among more than 120 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific "Ring of Fire".
After the eruption, the Disaster Mitigation Agency advised villagers and climbers to stay 4km from the crater and be aware of the risks of lava.