The Mount Agung volcano on Bali has erupted again, ejecting a 2,000-metre column of thick ash, and hurling lava down its slopes

The Mount Agung volcano on Bali has erupted again, ejecting a 2,000-metre column of thick ash, and hurling lava down its slopes.

The Indonesian geological agency's Agung-monitoring post said explosions from the mountain began just after 9:00pm on Monday and lasted more than seven minutes.

"Flares of incandescent lava" reached two kilometres from the crater, it said, setting fire to forests at high elevation on the mountain.

The volcano was periodically erupting ash, which was drifting west. The island's airport, to the south, was still operating normally.

National Disaster Mitigation Agency spokesman Sutopo Purwo Nugroho said the explosions on Monday night were "thunderous" and hurled white hot rocks from the crater.

It was the volcano's first explosive eruption since a dramatic increase in activity last year that temporarily forced the evacuation of tens of thousands of people.

The alert status for Agung was not from its second-highest level, and the exclusion zone around the crater remained at 4km.

Bali's international airport closed for half a day on Friday because of volcanic ash from Agung, disrupting travel for tens of thousands.