Rabies is on the rise on the Indonesian resort island of Bali and has left 12 people dead despite mass dog culls aimed at reining in an outbreak threatening the tourist industry.

The number of districts affected by the potentially fatal disease has more than tripled since August after first appearing in two districts in November last year, provincial veterinary agency chief Ida Bagus Alit told AFP.

"The number of areas affected by rabies is increasing. It has spread to seven districts, 13 subdistricts and 39 villages," Alit said.

Authorities have killed 28,509 stray dogs and vaccinated 115,593 dogs since the outbreak began, he said.

Provincial rabies control team official Ken Wirasandhi said 12 people, all of them Indonesian, had died in the outbreak.

Udayana University virologist Ngurah Mahardika said the local government had proven itself "not serious" in handling the rabies outbreak.

"The government has been very lax in abating the rabies spread. For example, the elimination of dogs is being done randomly and without coordination," he said.

Hindu-majority Bali is Indonesia's main tourist draw, famed for its beaches, temples and lush rice fields.

Australia, a key source of tourists to the islands, devotes a section of its travel advisory on Indonesia to warn its citizens to watch out for rabies in Bali and seek immediate treatment if bitten by animals.

The US embassy issued a warning to its citizens in Indonesia in January about rabies on Bali.