Mount Lewotobi Laki-Laki, a 1,584-metre-high volcano on the tourist island of Flores, erupted at 20:48 pm (1248 GMT), the volcanology agency said in a statement.
"The height of the eruption column was observed to be approximately 10,000 metres above the summit," the agency said.
There were no immediate reports of damages or casualties.
The eruption was triggered by a gas buildup in recent weeks, geological agency head Muhammad Wafid said in a statement.
He also warned of the possibility of hazardous lahar floods -- a type of mud or debris flow of volcanic materials -- if heavy rain occurs, particularly for communities near rivers.
Tourists and residents were told to avoid a six-kilometre radius around the crater.
Pictures shared by the country's geological agency showed volcanic lightning near the top of the ash plume.
Last month, the volcano spewed a colossal 18-kilometre tower of ash, scrapping 24 flights at Bali's international airport.
There were no immediate reports of cancelled flights after Friday's eruption.
Laki-Laki, which means man in Indonesian, is twinned with the calmer but taller 1,703-metre (5,587-foot) volcano named Perempuan, after the Indonesian word for woman.
Indonesia, a vast archipelago nation, experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire".
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