Thousands of people living in the shadow of a rumbling volcano on Indonesia's resort island of Bali have fled their homes, as fears grow that it could erupt for the first time in more than 50 years.

Mount Agung has belched smoke as high as 700 metres, sparking an exodus from the settlements near the mountain.

Disaster officials have warned that fresh activity at Mount Agung could see it blow its top.

Nearly 1,600 people died when Mount Agung last erupted in 1963.

It stirred to life again in September, prompting about 140,000 people to leave the area.

Many returned home after the volcano's activity waned, but thousands are now fleeing again.

Officials said around 30,000 people remain displaced.

The head of Indonesia's volcanology centre urged people to remain calm and said the mountain's alert level has not yet been raised.

Mount Agung lies some 75km from Bali's tourist areas, which attract millions of tourists every year.

Flights have not been affected so far, but officials have estimated that concerns about an eruption over the past few months have cost the island millions in lost tourism and productivity as many locals moved to shelters.

Indonesia lies on the Pacific "Ring of Fire", where tectonic plates collide, causing frequent volcanic and seismic activities.