At least six people died after a volcano in eastern Indonesia erupted several times overnight, officials said on Monday, raising the alert level to the highest of a four-tiered system.

Mount Lewotobi Laki-Laki, located on the popular tourist island of Flores, spewed a tower of ash and lava on nearby villages that were forced to evacuate.

"According to our coordination with the local authorities, six fatalities have been confirmed," Abdul Muhari, spokesman of the country's disaster management agency said on Monday in an interview on Kompas TV.

Video clips showed villages near the volcano covered by thick ash, with some areas on fire.

The country's volcanology agency raised the alert level to the highest mark, and told locals and tourists not to carry out activities within a seven-kilometre radius of the crater.

"There has been a significant increase in volcanic activity on Mount Lewotobi Laki-laki," it said in a press release.

It warned there was a potential for rain-induced lava floods and told locals to wear masks to avoid the effects of volcanic ash.

The mountain had several major eruptions in January, prompting authorities at the time to raise the alert status to the highest level and evacuate at least 2,000 residents.

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. (AFP)