It was the fourth eruption since the 2,451-metre-high volcano in North Sumatra province erupted Aug 29 after more than 400 years of inactivity. The fresh eruption prevented more than 23,000 residents from returning to their homes on its slopes.
The eruption early Tuesday was followed by thunder-like sounds heard up to eight km from the crater, the Volcanology and Geological Disaster Mitigation Center said. It occurred at around 12:37 a.m. (1737 GMT Monday) and caused power outages in nearby villages.
Local media reported that the volcanic ash had reached as far as Berastagi district, about 25 km from the volcano. Thick dust in villages on the slopes limited visibility to around five metres. The volcano's fresh eruption also reportedly forced President Susilo Bambang Yudhoyono to delay his departure from Medan to Jakarta.
Yudhoyono spent the night in the North Sumatran capital after he visited the residents of evacuation centres and offered more aid. Indonesia has the highest density of volcanoes in the world with about 500 within the 5,000-km-long archipelago nation. Nearly 130 are active and 69 are listed as dangerous.