Mount Lewotobi Laki-Laki, a 1,703-metre (5,587-feet) twin volcano located on the popular tourist island of Flores, erupted shortly before midnight, forcing authorities to evacuate several villages.
Abdul Muhari, spokesman of the country’s disaster mitigation agency (BNPB), confirmed the death toll at a press conference, adding that 10,295 people had been affected by the eruptions.
Buildings near the volcano were covered by thick ash while some wooden homes caught fire, and the ground was pockmarked with holes caused by flying molten rocks.
The volcanology agency hoisted the highest alert level and told locals and tourists not to carry out activities within a seven-kilometre (4.3-mile) radius of the crater.
“We didn’t hear any warning signs because it started with thunder and lightning,” said Petrus Muda Turan, head of a village on the Catholic-majority island, adding that the dead included a baby and a young nun.
There were multiple tremors and eruptions at the volcano last week, sending columns of ash between 500 and 2,000 metres (6,500 feet) into the sky several days in a row.
Indonesia, a vast archipelago nation, experiences frequent eruptions due to its position on the Pacific “Ring of Fire”, an area of intense volcanic and seismic activity.