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.

The 2,600-meter (8,530-foot) -high mountain in North Sumatra province has sporadically erupted since September 2013 after being dormant for three years.

National disaster management agency spokesman Sutopo Purwo Nugroho said the status was raised to the highest level before midnight Tuesday.

Nugroho said Wednesday that the volcano's increased activity the past two days had made it unstable.

The agency urged residents living within a radius of 7 kilometers (4 miles) south and southeast of the crater to evacuate.

Mount Sinabung is among more than 120 active volcanoes in Indonesia, which is located on the Pacific "Ring of Fire."