Indonesia has raised the alert for the Mount Sinabung volcano in Sumatra to the highest level.
The status was raised from "stand-by" to "caution" - the highest alert for volcanic activity - on Sunday.
Airlines have been advised not to fly near the area.
People have also been warned to stay at least 5km from the crater.
Mt Sinabung has been showing signs of life since September, after being dormant for three years. .
In a statement, disaster management officials said more than 15,000 villagers have been moved to temporary shelters.
The BBC reports Mount Sinabung is one of around 130 active volcanoes in Indonies. Before 2010, Mount Sinabung had not erupted in 400 years.