Indonesia's holiday island of Bali reopened to foreign tourists after 18 months of pandemic hiatus on Thursday, but the island is lacking one crucial ingredient: international flights.

Tourism-reliant Bali is scheduled to reopen on Thursday and though its Ngurah Rai international airport has carried out simulations preparing for tourists to return, it is not expecting much to happen soon.

"So far there is no schedule," said Taufan Yudhistira, a spokesman for the airport.

Indonesia's tight immigration measures during the pandemic have devastated the island, with widespread closures of hotels, shops and businesses.

The government is eager to revive Bali's beleaguered tourism industry in response to a sharp fall in new coronavirus cases since July, when Indonesia was Asia's COVID-19 epicentre.

But details about the reopening, such as visa requirements and which countries they apply to, have so far been patchy.

Indonesia only confirmed the 19 eligible countries in a statement late on Wednesday, which include China, India, Japan, South Korea and New Zealand, and several countries from Western Europe and the Arabian Gulf.

The move follows Thailand's calibrated reopening that began in July with much fanfare, with the islands of Samui and Phuket welcoming vaccinated tourists from multiple countries, with hundreds on the opening days.

Vietnam plans to welcome foreigners to its Phu Quoc island next month.

But some Indonesian tourism industry representatives say Bali's reopening plan not matched by demand.

I Putu Astawa from the Bali tourism agency said hotel reservations were few.

"Not yet because the timing is so sudden," he said, when asked about a spike in bookings. "They need time to take care of visas and flights."

As well as requiring Bali visitors to be vaccinated against COVID-19, Indonesia has stipulated they must spend their first five days in quarantine, a measure rival tourism markets are phasing out.

"We are ready to accept tourists who visit Bali, but certainly it does not mean all the guests suddenly visit Bali," said Ida Bagus Purwa Sidemen, executive director of the island's hotel and restaurant association.

"At the earliest, by the end of the year we can evaluate whether the situation has improved."

In a video released on the president secretariat's YouTube channel to mark the reopening on Thursday, Bali Governor I Wayan Koster said reviving tourism was essential for the island.

"It is very much in our interest for tourism to recover because 54% of Bali's economy relies on tourism sector," he said.