Indonesians have begun casting their ballots in only the country's second direct presidential elections as polling kicked off in the eastern-most province of Papua.
Some 500,000 polling stations will be open from 7am until noon across the country with partial "quick counts" expected a few hours after polls close at 05:00 GMT.
About 176 million people have registered to vote in Southeast Asia's biggest economy and the world's third-largest democracy.
In Papua, security was stepped up ahead of the polls on Wednesday, but there were no reports of related violence.
Legislative elections in April were marred by clashes in parts of Papua, a resource-rich region two hours ahead of the Indonesian capital, Jakarta, where a low-level secessionist movement has simmered for years.
Yudhoyono win expected
|Security was boosted across the country ahead of the second democratic elections [Reuters]
Simon Tabuni, an election official in Papua, said he hoped people would "come to vote for the best head of state who is able to create peace and prosperity".
Opinion polls point to a decisive victory for Susilo Bambang Yudhoyono, the incumbent, against his challengers, Jusuf Kalla, the vice-president, and Megawati Sukarnoputri, the opposition leader.
Megawati was president from 2001 to 2004 and her father, Sukarno, was Indonesia's first president.
Kalla heads the Golkar party and has teamed up with General Wiranto, who helmed the country's armed forces during the Suharto era.
Andi Mallarangeng, Yudhoyono's campaign spokesman, said on the eve of the election that the president's team was "optimistic our candidate will win in a single round based on recent poll results", adding that people "want the continuation of stability in politics, security and economy".
Voters will be looking for their candidates to make greater strides against endemic corruption and widespread poverty - major challenges facing the predominantly Muslim country of 235 million.
With around 100 million Indonesians living on less than $2 a day, capturing the vote of the poor masses has been a top priority throughout the campaign.
Yudhoyono, a former army general, has led most opinion polls and is predicting an easy first-round victory, but a survey released on Saturday showed Megawati with a 17-percentage point lead as the campaign period officially closed.
However, another poll showed Yudhoyono with 63 per cent support, enough to gain a second term with a clear majority of the country's 170 million eligible voters.
Tens of thousands of supporters wearing the blue and white colours of Yudhoyono's Democratic party packed into a stadium in the capital Jakarta on Saturday to hear the president give his last speech of the campaign.
"I'm sure that in the next five years, Indonesia won't just rise but also will become more developed with an even bigger success," he said.
"God willing, in five years the world will say 'Indonesia is rising, Indonesia is emerging'."
Meanwhile, Megawati warned supporters to beware of electoral fraud as she campaigned in central Java.
"They think the people are stupid, can be manipulated, intimidated and terrorised," she was quoted as saying by the Kompas news website, repeating her claims that electoral officials are biased towards Yudhoyono.
Megawati, who leads the Democratic People's party of Struggle, has a strong following as the daughter of independence hero Sukarno and was the figurehead of the opposition against Suharto's regime in the late 1990s.
|Megawati and Wiranto have warned of 'electoral irregularities' before the vote [AFP]
She became president of the world's third-largest democracy, but her administration was widely known for inaction and corruption and she was ousted in a landslide by Yudhoyono in 2004.
The "dark horse" in the race is Kalla who has trailed in opinion polls but has proven to be a tough competitor on the campaign trail.
With his motto of "the faster, the better", Kalla and Wiranto have attacked Yudhoyono as a "neo-liberal" and championed a philosophy of economic "self-reliance".
Megawati also advocates a "people-centred economy" and her running mate, former special forces commander Prabowo Subianto, has openly compared his brand of economic nationalism to that of Hugo Chavez, the Venezuelan president.
By contrast, Yudhoyono chose Boediono, a Western-educated economist and former central bank governor, as his vice presidential candidate, winning praise from the markets but opening himself to the "neo-liberal" label.