Thousands of people on Java island are being evacuated after Mount Kelud erupted, an Indonesian official said.
Muhammad Hendrasto, head of the Volcanology and Geological Disaster Mitigation Centre, said the volcano in Kediri regency erupted about 90 minutes after authorities raised its status to the highest level.
He urged about 200,000 people living in 36 villages within the danger zone of six miles (10km) from the crater to evacuate.
A series of huge blasts unleashing stones and gravel caused panic among villagers who immediately fled to safer areas.
In 1990, Kelud spewed searing fumes and lava that killed more than 30 people and injured hundreds. In 1919, a powerful explosion that reportedly could be heard hundreds of miles away killed at least 5,160.