JAKARTA -- Long lines have formed in many gas stations across a number of regions in Indonesia, including resort island Bali, where fuel shortages are affecting tourists and local residents alike.

Elisa Valenta, who just came back from Bali to Jakarta on Tuesday, told Nikkei Asia that she struggled to find transportation to Ngurah Rai Airport on the southern part of the island to catch her flight back to the Indonesian capital, as many taxis and ride-hailing vehicles ran out of fuel.

Some gasoline products were "out of stock" and "customers had to queue," said Valenta, who eventually made it to the airport after a friend picked her up on a motorbike and took her along with her luggage. Bali resident Abdi Wirajaya said gasoline shortages have afflicted the island over the past few days, with a number of gas stations completely running out of fuel and others offering only a non-subsidized product lineup called Pertamax.

Most gas stations across Indonesia operate under state energy conglomerate Pertamina, which last month raised prices of two Pertamax products by 7% to 15% to at least 19,150 rupiah ($1).

The increases have prompted many consumers to switch to cheaper products including subsidized Pertalite, sold at 10,000 rupiah per liter, causing the shortages and long gas station queues. Wirajaya said his workplace considers allowing employees to work from home. Another Bali resident, Madeline Kisarani, told Nikkei Asia that she and her friend had to hitchhike to get to work.

She said some resellers took advantage of the situation, offering gasoline up to five times their original prices at roadside stalls. While fuel shortages only hit Bali this week, over the past few months long lines at gas stations have become a common sight across many Indonesian regions on Java, Sumatra, Borneo and Sulawesi islands. Observers said the number of areas affected is expanding, with long queues reported recently in several cities in East Java, South Sulawesi, Lampung and West Kalimantan provinces, among other places.

At several major gas stations along the Trans-Java toll road, diesel stocks have also run out, forcing logistics vehicles and intercity buses to wait longer for refill or switch to non-subsidized diesel, which costs much more.

Signboards at a Pertamina gas station in Jakarta show subsidized and non-subsidized gasoline and diesel products.

Ahad Rahedi, a communication manager for East Java and Bali at Pertamina Patra Niaga, the distribution arm of Pertamina, attributed delays in fuel deliveries partly to the Middle East conflict mainly between the U.S. and Iran.

Southeast Asia's largest economy relies on imports for much of its oil needs, consuming about 1.6 million barrels per day against domestic crude and condensate output of roughly 600,000 bpd.

Rising crude prices have also made spot cargoes more expensive while Indonesia struggles to reverse declining domestic production.

Benchmark Brent futures have surged again after going down to a four-month low of around $70 per barrel in July amid the escalating conflict in the Middle East. On Wednesday, it hit $106 per barrel, following deadly attacks over the weekend on a major Saudi Arabia airport by Yemen's Iran-backed Houthi rebels.

"Another [cause for the fuel shortages] is changes ... in the public consumption pattern," Rahedi told Nikkei Asia, referring to many consumers' switch from Pertamax to Pertalite. Pertamina Patra Niaga said in a statement Monday that it has delivered 18,000 kiloliters of Pertalite and 2,500 kiloliters of Pertamax to Bali, with plans to ship a total of 26,200 kiloliters more fuel this week.

Bali consumes approximately 2,200 kiloliters of Pertalite daily, the company said. Rahedi said it "will continue to optimize supplies to gas stations while taking into account inventory levels and consumption in each region."

Laode Sulaiman, director general of oil and gas at the Ministry of Energy and Mineral Resources, attributed the fuel shortages to distribution problems, including high sea waves preventing vessels from docking and drying rivers also hampering delivery. "What I'm explaining are the causes of the problem in general, not just in Bali," he told reporters in Jakarta on Wednesday.

Fabby Tumiwa, CEO of think tank the Institute for Essential Services Reform, said Pertamina "faces growing pressure on its cash flow."

The national oil company is bearing the brunt of rising subsidy costs as the government mostly tries to keep domestic fuel prices low over concerns of social unrest, despite surging global crude prices. It has to cover price gaps upfront before the government reimburses it later, with the reimbursement often hit by delays. "Recurring fuel shortages are not merely a distribution problem," Tumiwa told Nikkei Asia.

"They're a warning sign of vulnerabilities in national energy security that require immediate action."