Volcano closes Bali airport for second day

Bali's airport has been closed for a second day as plumes of ash continue to gush from a rumbling volcano.

Thousands of tourists, mostly Australians, are stranded at Ngurah Rai International Airport - with flights grounded until at least 7am on Wednesday.

Experts have raised the alert level to its highest, warning that Mount Agung could erupt at any moment.

Tens of thousands of frightened locals have fled their homes, but it is feared that thousands more have not evacuated because they feel safe or do not want to abandon livestock.

"Plumes of smoke are occasionally accompanied by explosive eruptions and the sound of weak blasts that can be heard up to seven miles (12km) from the peak," the Disaster Mitigation Agency said in a statement after raising the alert level from three to four.

"The potential for a larger eruption is imminent," it warned.

Mount Agung is one of more than 120 active volcanoes extending the length of Indonesia that sits on the so-called Pacific Ring of Fire.

It last erupted in 1963, killing about 1,600 people.