According to Farid Ruskanda Bina, head of the Mt Lokon observation post in Tomohon, increasing seismic activity was recorded shortly before the eruption. The volcano was now spitting incandescent materials to a height of up to 1200 meters into the sky.
Eighteen Indonesian volcanoes are on "alert" status, two of which are at Alert Level 3, which is called "Siaga", the Volcanology and Geology Disaster Mitigation Center says.
Center head Surono in July said that the erupting Mount Lokon in North Sulawesi and Mount Ibu in North Maluku were the two volcanoes at Siaga status.
The center has adopted four levels of alert status: "Normal" (Level 1), "Waspada" (Level 2), "Siaga" (Level 3) and "Awas" (Level 4).
Surono said the conditions at Mt Lokon and Mt Ibu were currently considered most worrisome because they had been consistently erupting searing clouds affecting a radius of 2.5 kilometers.
According to him, the eruptions had not yet endangered people living around the volcanoes.
"The eruptions are heading west, while people are concentrated in east," he said as quoted by tempointeraktif.com.
Surono added that 16 other volcanoes were at Level 2 alert status, "Waspada", including Mt. Papandayan and Mt. Guntur in West Java.
"Locals have reported several quakes," he said.
Surono said that President Susilo Bambang Yudhoyono had summoned him on Saturday to report the volcanoes` status and the center`s preparations to anticipate possible disasters.
Ideally there should be an expert monitoring the activities of each volcano in Indonesia, as is the case in Japan, he said.
"Currently an expert handles five mountains."