Nearly 3,000 people have been evacuated from their homes after Indonesia upgraded the threat posed by a volcano on Sumatra to the highest possible level, an official said Thursday.

Authorities raised the alert status of Mount Sinabung -- a highly active volcano on Indonesia's westernmost island -- late Tuesday after a "sharp rise" in activity, said national disaster management agency spokesman Sutopo Purwo Nugroho.

The amount of hot ash, smoke and rock spewing from the volcano has ramped up significantly since Sunday, with lava visible at the crater, the Mount Sinabung Observation Station chief Armen Putra said.

Military based in the area told AFP that soldiers and police Wednesday evacuated 2,730 residents from four villages within a danger zone around the south and southeast of the volcano.

"Volcanic activity is still high today, triggering tremors," said district military commander Lieutenant-Colonel Asep Sukarna.

"Yesterday we worried that the volcano would send hot ash clouds down over the villages, so we moved 2,730 people to a safer place."

People were aware of the danger and left in an orderly fashion, he said, adding that there were no further orders at this stage to evacuate other villages.

Those displaced are now in temporary shelter 13 km (8.1 miles) from the volcano.

Nearly 10,000 people have now had to evacuate their homes since Sinabung burst back into life in 2013 after a period of inactivity.

While some were able to return once volcanic activity died down, others have been forced to remain in shelters.

A massive eruption in February 2014 killed at least 16 people and sent thousands more fleeing for safety.

Sinabung is one of 129 active volcanoes in Indonesia, which sits on the Pacific Ring of Fire, a belt of seismic activity running around the basin of the Pacific Ocean.

The country's most active volcano, Mount Merapi in central Java, killed more than 350 people in a series of eruptions in 2010.