The volcano was sending ash some 8 kilometers (4.9 miles) into the sky Sunday and forcing more residents of the Karo area of North Sumatra to evacuate.
"This is Sinabung's highest level of activity and the intensity of the eruptions continues to increase," said Hendrasto, head of the Volcanology and Geological Disaster Mitigation Center.
The Karo government posted its highest level of alert and announced that the number of people evacuated had doubled to 11,618 residents of 19 villages.
The Jakarta Post said health officials warned residents around the volcano to limit their outdoor activities and wear sun glasses and masks to protect against falling ash if they had to venture out of their homes.
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