The mountain located in Halmahera island of North Maluku province has increased its activities since Monday morning and its status has been risen to top alert, said Muhammad Hendratno, the head of observation unit of the Indonesian Volcanology Agency.
A television footage of Metro TV showed that thick smoke went out up to thousands meters high from the crater of the mountain.
Hendratno said that the explosion had spewed smoke up to over 3, 500-meter high, containing ashes which was very dangerous to be breathed.
The mountain has erupted for several times and the strongest eruption was the one after midday Monday, a spokesman of the local administration of Halmahera regency in the island Kalbi Rasid told Xinhua on telephone.
The eruption feared residents living in eight villages at the slope of the mountain in radius of eight kilometers and some of them left their homes, he said. However, some of the residents still lived in tents located in safe area, more than eight kilometers from the mountain, he added.
He said that should the situation be getting worse, all of them must be evacuated.
Preparation for evacuation had been carried out, scores of policemen and soldiers have been involved, and a number of vehicles were also prepared for picking up the evacuees, said Rasid.
Indonesia is laid at a vulnerable zone so called the Pacific Ring of Fire where two continental plates meet, causing frequent volcanic movements.
Indonesia has 129 active volcanoes and 66 of them are located in high-density-population Java and Sumatra island, according to the meteorology agency.