Indonesia has raised the alert status of Sinabung volcano in the western part of the country to the highest level following a sharp increase in activity, an official said.
The 2,600m-high mountain in North Sumatra province has sporadically erupted since September 2013 after being inactive for three years.
The volcano's status was raised to the highest alert level before midnight Tuesday, said national disaster management agency spokesman Sutopo Purwo Nugroho.
The level means an eruption is possible within days.
He said the volcano's increased activity the past two days had made it unstable.
The agency urged residents living within a radius of four miles south and south east of the crater to evacuate.
The volcano had been dormant for four centuries before springing to life in August 2010, killing two people and forcing 30,000 to flee. An eruption in February 2014 killed 16 people.
Mount Sinabung is among more than 120 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific "Ring of Fire", an arc of volcanoes and fault lines encircling the Pacific Basin.