A powerful burst of hot ashes erupted from the rumbling Mount Sangiang in West Nusatenggara province, Xinhua reported.
The volcano, located in a small island of Bima district, spewed ashes into the sky at 3.55 p.m., Muhammad Hendrasto, head of the National Volcanology Agency, said.
"Scores of farmers cultivating the land in the island, seven km from the crater, have been told to leave the area since this morning. And they have been warned not to re-enter the island during the eruption period," he told Xinhua by phone.
Authorities had put Mount Sangiang on high alert since June 14, 2013, Hendrasto said.
"With this eruption, we are likely to raise the alert level to the second highest," he said.
So far, no similar order had been issued for evacuation of those living in the nearby island, according to Hendrasto.
Mount Sangiang is among 129 active volcanoes in Indonesia, which is prone to seismic upheaval due to its location on the Pacific "Ring of Fire", an arc of volcanoes and fault lines encircling the Pacific Basin.
In February, more than 15 people were killed and tens of thousands of others were internally displaced when the volcano erupted intermittently.