Indonesian authorities raised the alert for Mount Semeru volcano to the highest level on Wednesday after a series of eruptions, prompting evacuations. The volcano is the highest peak on Java, the most densely populated island in Indonesia.

Mount Semeru in East Java province unleashed avalanches of searing clouds of hot ash and a mixture of rock, lava and gas that travelled up to 7 kilometres down its slopes several times since midday to dusk, while a thick column of hot clouds rose 2 kilometres into the air, Indonesia's Geology Agency said in a statement.

The eruption throughout the day blanketed several villages with falling ash, forcing authorities to raise the volcano's alert level twice, from the third-highest level to the highest, the agency said. No casualties have been reported so far.

More than 300 residents in the three villages most at risk in the district of Lumajang had been evacuated to government shelters.

Semeru, also known as Mahameru, has erupted numerous times in the past 200 years. Still, as is the case with many of the 129 active volcanoes in Indonesia, tens of thousands of people continue to live on its fertile slopes.

Indonesia, an archipelago of more than 270 million people, sits along the Pacific “Ring of Fire,” a horseshoe-shaped series of fault lines, and is prone to earthquakes and volcanic activity. (AP)