Indonesia's Mount Semeru on Saturday erupted throwing hot ash and smoke around 5.6km into the air.

There were no immediate evacuations, but the National Disaster Mitigation Agency warned people who live in the villages on the slopes of the mountain to be vigilant in looking for signs of danger.

Indonesia's Volcanology and Geological Hazard Mitigation Centre did not raise Semeru's alert status, which already had been at the third-highest level since it began erupting in May.

The volcano spewed hot ash 3,000 meters 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.

Government seismologists monitor more than 120 active volcanoes.

A strong earthquake shook Indonesia’s Sulawesi island early Friday, killing at least 46 people.