Mount Sinabung, in the north of the island of Sumatra, began erupting around midnight after rumbling for several days, prompting some villagers to panic before the mass evacuation got under way.

Indonesia is on the so-called Pacific Rim of Fire, an arc of volcanoes and geological fault lines triggering frequent earthquakes around the Pacific Basin. The eruption triggered the highest red volcano alert.

Two people died, one from breathing problems and the other from a heart attack, and two suffered injuries in road accidents as trucks, ambulances and buses were mobilized in the rescue operation.

Authorities took at least 12,000 people from high risk areas on the slopes of the 2,460-meter volcano to temporary shelters. Local TV showed women and children wearing face masks in cramped tents.

The area around the volcano is largely agricultural.

The eruption has not damaged roads or bridges. The nearest big city is Medan where there were no disruptions to flights.