Lewotobi Laki-laki, located on Flores island in eastern Indonesia, spewed volcanic ash between three to 5.5 kilometres high on Sunday, the nation's volcanology agency said.
"Our analysis showed that the activities of Mount Lewotobi Laki-laki are still high so we raised the status level starting on Sunday at 8pm (10pm AEST)," the agency's head Muhammad Wafid said in a statement late on Sunday.
Images shared by the agency showed clouds of thick grey ash billowing from the crater. Rumbling noises with low to high intensity were heard from the nearest monitoring post during the eruption, Wafid added.
On Monday morning, the volcano erupted again, belching 1.2km high ash clouds.
The agency said a six-kilometre radius from the crater must be cleared and warned residents of the risk of cold lava flow from the crater after heavy rains.
There have not been any evacuation of residents or flight cancellations due to the eruptions so far, said Heronimus Lamawuran, a local government official.
In March, an eruption at Lewotobi Laki-laki forced some airlines to cancel and delay flights into Bali, including Australia's Jetstar and Qantas Airways.
At least nine people were killed and thousands were evacuated when the volcano erupted in November 2024.
Indonesia sits on the "Pacific Ring of Fire", an area of high seismic activity atop multiple tectonic plates.
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