Indonesian Defense Minister Prabowo Subianto appeared poised to win Wednesday's presidential election in a single round, according to unofficial tallies.
Independent pollster Litbang Kompas said that Subianto was leading with nearly 60% of the vote, based on over half of the votes counted at a sample of polling stations across the country. Two other pollsters, Poltracking and Cyrus Network-CSIS, also reported similar results.
His rivals, Anies Baswedan, the former governor of Jakarta, and Ganjar Pranowo from the Indonesian Democratic Party of Struggle, had just under 23% and 17.3%, respectively, according to Kompas.
After the numbers were published, a spokesman for Ganjar said the politician's team had received reports of "structural, systematic and massive fraud" and was investigating them. Separately, Ganjar said he and his aides will "wait for election results."
Private pollsters count the votes at a sample of polling stations around the country. These are called "quick counts." In previous elections, counts by reputable pollsters have proven accurate. Official results are not expected for several weeks.
World's biggest single-day election
Polls have closed in Indonesia for the world's biggest single-day election that will see a new president succeed Joko Widodo, also known as President Jokowi. The voters are also deciding on new lawmakers and parliamentarians.
Voting took place across three times zones with polling stations opening at 7:00 a.m. (2200 GMT) in the easternmost region of Papua and closing at 01:00 p.m. (0600 GMT) at the other end of the country in jungle-clad Sumatra.
Thunderstorms caused flooding in some parts of the capital, Jakarta, with Reuters news agency reporting that dozens of polling stations had been affected.
Who are the main contenders?
The race for the presidency has seen three main candidates emerge. According to opinion polls ahead of the vote, the man leading the race is Prabowo Subianto from the Gerindra Party, a former military commander who currently serves as the Minister of Defense.
Prabowo is up against Ganjar Pranowo from the Indonesian Democratic Party of Struggle and Anies Baswedan, the former governor of Jakarta.
Indonesia is the world's third-largest democracy with around 205 million voters eligible to cast ballots.
What's at stake?
As Southeast Asia's largest economy, Indonesia has experienced stability and growth under Jokowi's leadership. All three presidential contenders have made similar promises to continue in that vein.
Probowo is the only candidate with ties to the era of Suharto dicatorship, a time marked by brutality and corruption. He was a special forces commander during that period and has been accused of human rights atrocities, which he strongly denies.
There have been concerns that a Probowo presidency could see a backslide towards Indonesia's authoritarian past.
Such changes would have ramifications beyond Indonesia, as Jakarta wields a significant diplomatic influence among its Southeast Asian neighbors and boasts strong trade relationships with China and the US.