Mount Semeru, the highest volcano on Indonesia's most densely populated island of Java, has erupted, spewing ash and hot clouds as far away as 4.5 kilometres.
There were no immediate evacuations, but the National Disaster Mitigation Agency has warned people who live in the villages on the slopes of the mountain to be vigilant in looking for signs of danger.
Agency spokesperson Raditya Jati said people around the river basin on the slopes of the mountain should beware of high rainfall that can trigger lava floods.
"Residents have been advised to remain alert for a potential disaster," he said on Saturday.
Indonesia's Volcanology and Geological Hazard Mitigation Center did not raise Semeru's alert status, which already had been at the third-highest level since it began erupting in May.
The volcano erupted in early December, triggering panic among villagers.
Indonesia, an archipelago of more than 250 million people, sits on the Pacific "Ring of Fire" and is prone to earthquakes and volcanic eruptions.
Government seismologists monitor more than 120 active volcanoes.
A strong earthquake shook Indonesia's Sulawesi island early on Friday, killing at least 46 people.
Australian Associated Press