A volcano that had been dormant for more than four centuries erupted for the second day in a row, spewing white clouds of smoke and ash more than 2,000 metres into the air.
Thousands of people living along the slopes of Mount Sinabung in Indonesia's North Sumatra province have been evacuated to emergency shelters, mosques and churches.
Their abandoned villages and crops are blanketed in heavy, grey soot.
Mount Sinabung last erupted in 1600, so observers don't know its eruption pattern and are monitoring it closely for more activity. They raised the volcano's alert to the highest level after its first blast yesterday, which followed days of rumbling.
"The problem is, we really have no idea what to expect," a government volcanologist said. "We don't know what set it off, how long it will continue or whether we should expect pyroclastic flows."