At least 100,000 foreign tourists are expected to gather at a dozen hot spots across Indonesia for the rare total solar eclipse tomorrow morning.

At the weekend, hundreds of visitors arrived in places like the island of Belitung, off the east coast of Sumatra, where Indonesia's President Joko Widodo will join some 7,000 locals and tourists to catch what has been touted as the country's biggest tourism highlight of the year.

The total solar eclipse will sweep across 12 of the country's 34 provinces, before heading out in the direction of the Pacific Ocean, and end in the north of Hawaii.

The natural phenomenon occurs when the moon passes exactly between the Sun and the Earth, covering the solar face entirely.

"Indonesia is special as it is the only country that the total solar eclipse can be observed from land," National Institute of Aeronautics and Space of Indonesia chairman Thomas Djamaluddin told The Straits Times.

"You will see a white light around the sun and tongues of flames. It's a spectacular sight," he said, adding that, in the daytime darkness, some brighter stars may be visible.

The last time a total solar eclipse passed over Indonesia was two decades ago on Oct 24, 1995. The next solar eclipse will be on April 20, 2023.

British car businessman John Baistow, 50, was among those who flew in to Indonesia yesterday to watch the spectacle.

He said he wanted to fulfil one item on his bucket list after witnessing a "fantastic" partial solar eclipse in England in 2014. "I Googled where the next eclipse is and, fortunately for me, it coincided with my love for this wonderful country, Indonesia," he told The Straits Times.

Mr Baistow said he had been prepared to spend the next few nights on the beach because all the hotels were fully booked.

"But the airport security guard offered to take me into town and stay at his home," he said.

Tourism receipts, from hotels, retailers and travel agencies, are set to reach almost 200 billion rupiah (S$21 million), said the Tourism Ministry's assistant deputy for archipelago tourism development Putu Ngurah.

"The Indonesian government began promotions a year ago and has spent 15 billion rupiah on special events such as traditional dances, live bands and dragonboat races to be held across the country," he said.

"We went all out, and why not? This is a rare phenomenon."