Mount Lewotobi Laki-Laki, a 1,584-metre-high twin-peaked volcano on the tourist island of Flores, erupted at 5:35 pm local time (0935 GMT), the volcanology agency said in a statement.

"The height of the eruption column was observed at approximately 10,000 metres above the summit. The ash column was observed to be grey with thick intensity," it said, after the alert level was raised.

There were no immediate reports of damages or casualties.

Geology agency head Muhammad Wafid said residents and tourists should avoid carrying out any activities within at least seven kilometres of the volcano's crater.

But he 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 to rivers.

He also urged residents to wear face masks to protect themselves from volcanic ash.

National Disaster Mitigation Agency (BNPB) spokesman Abdul Muhari said in a statement late Tuesday that at least one village had to evacuate, without providing numbers, and ash rain was reported in several villages outside the exclusion zone.

The spokesman called on residents around the volcano "to evacuate to safe locations" as tremors were still being detected, which indicated ongoing volcanic activity.

Mount Lewotobi Laki-Laki erupted multiple times in November, killing nine people and forcing thousands to evacuate, as well as the cancellation of scores of international flights to Bali.

There were no immediate reports of cancelled flights after Tuesday'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".