Indonesian authorities are preparing to divert flights to 10 airports across the country in case an increasingly active volcano on the holiday island of Bali erupts and disrupts travel.

Officials have warned that Mount Agung in eastern Bali could erupt at any time, prompting several countries, including Australia and Singapore, to issue travel advisories for one of the world's most popular tourist destinations.

"Ten airports will serve as alternatives for flights bound for Bali's Ngurah Rai airport in case it is closed because of volcanic ash," Transportation Minister Budi Karya said in a statement on Wednesday.