A volcano on the Indonesian tourist island of Bali erupted for the second time in a week, disrupting international flights even as authorities said the island remained safe.

The ash column from Mount Agung rose 4,900 feet following an eruption that began at about 5.30pm on Saturday, and has continued for several hours, said Indonesia's National Disaster Mitigation Agency.

Villages close to the volcano were coated in a thin layer of ash.

Ash clouds were moving to the southwest, away from the island's international airport, which remained open, said disaster agency spokesman Sutopo Purwo Nugroho.

The volcano's alert status has not been increased from the second highest level.

Australian airline Jetstar cancelled nine flights to or from Bali on Saturday evening and said it was delaying several Sunday flights to give more time to monitor the situation.

Sutopo said that in total, eight international flights to Bali and 13 departing from the island were cancelled. He said about 2,000 passengers were stranded at the airport.

The volcano's last major eruption in 1963 killed about 1,100 people.

Authorities say anyone still in the exclusion zone around the volcano, which extends 4.5 miles from the crater in places, should leave the area.

About 25,000 people have been unable to return to their homes since September, when Agung showed signs of activity for the first time in more than half a century.

Indonesia sits on the "Pacific Ring of Fire" and has more than 120 active volcanoes.