Mt Sinabung in North Sumatra threw an ash cloud thousands of metres into the air on Tuesday in its most violent eruption yet.
“Its latest eruption was double the previous outburst and we recorded a tower of ash reaching 5,000 metres,” government volcanologist Agus Budianto said.
He said the 2,460-metre volcano erupted at 12.23am and it was felt about eight kilometres away.
More than 20,000 people have fled their homes since the volcano first erupted late August and remain in emergency shelters.
President Susilo Bambang Yudhoyono visited the area on Monday, inspecting disaster management operations and asked the refugees to be patient.
Volcanologists said Sinabung’s long dormant period of over 400 years has made it highly unpredictable.