Yogyakarta: Indonesia's most active volcano erupted on Tuesday, spewing sand and pyroclastic material and sending massive smoke-and-ash column as high as 6000 metres into the sky.

The eruption of Mount Merapi on the main island of Java also unleashed searing gas clouds 2 kilometres down its slopes, said Indonesia's Geology and Volcanology Research Agency on its website.

Mount Merapi spews volcanic material into the air in Sleman, Indonesia. Credit:AP

The agency said villagers living on Merapi's fertile slopes were advised to stay 3km from the crater's mouth as the ash made the rain thick and muddy in several villages.

Witnesses said the sound was heard 30km away. The agency did not raise the alert status of Merapi, which already was at the third-highest level due to its ongoing activity.

The 2968-metre mountain is the most active of 500 Indonesian volcanoes. It has rumbled and generated dark hot clouds since last year. Its last major eruption in 2010 killed 353 people.

Indonesia, an archipelago of 240 million people, is prone to earthquakes and volcanic activity because it sits along the Pacific "Ring of Fire", a horseshoe- shaped series of fault lines around the ocean.

AP