Joko Widodo, Indonesia's President, is poised to win a second term, based on unofficial election results released within hours of polls closing.

The 57-year-old, known as Jokowi, had an 11 point lead over his rival Prabowo Subianto, 67, with 76.8 per cent of the votes counted, according to the Jakarta-based Centre for Strategic and International Studies.

Official results from the world's largest single-day poll will not be announced by the election commission until May 22, but initial counts from reputable companies in past elections have proved to be reliable indicators.

Speaking to supporters, Widodo acknowledged the exit poll results but called on all parties to wait for the official tally. He urged all members of the public to reunite following the bitterly contested presidential race.

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His opponent, Prabowo, a nationalist former military general, also asked his supporters to "remain calm" and "unprovoked from committing anarchy".

However, he immediately disputed reports that Widodo was in the lead and claimed to have won 55.4 per cent of the vote in exit data collected from 5000 polling stations.

He alleged that "many ballots were not delivered to the polling stations, many polling stations were opened [late] at 11am. There were many anomalies".

The presidential race was a rematch of the 2014 contest when Prabowo claimed victory on election day, before contesting the results at the Constitutional Court, which confirmed Widodo's win.

The delay in issuing the official results is a reflection of the vast logistical operation behind holding a presidential and parliamentary election on the same day across three time zones and an archipelago of about 17,000 islands.

More than 192 million Indonesian voters were eligible to cast their ballots for a record 245,000 candidates.

Analysts suggested there was not a huge variation between the economic agendas of the two leading presidential nominees, leading them both to lurch to the right to court conservative Islamic forces in an effort to garner more votes.