JAKARTA (BLOOMBERG) - Indonesian President Joko Widodo is on course to win a second term as he led his challenger by about 12 percentage points midway through an official tally of votes, confirming earlier results from about a dozen private pollsters.

Mr Joko, also known as Jokowi, secured 56.2 per cent of the votes, compared to 43.8 per cent polled by his challenger Prabowo Subianto, with 50 per cent of the ballots tallied, the General Elections Commission said, citing an online count of votes cast in the April 17 election.

The authority has until May 22 to complete the counting of the ballot papers.

The validation of the tally from private pollsters may be a blow to former Suharto-era general Prabowo, as he has disputed the unofficial counts to claim a win.

While Mr Joko has urged people to be patient and wait for the election commission to complete the counting of ballots, Mr Prabowo has claimed "massive fraud" in the election, a charge the government termed as "unfounded" and meant to "de-legitimise the government and election organisers".

Indonesia held its first simultaneous presidential and legislative elections, with more than 245,000 candidates in fray for about 20,000 positions.

The turnout was more than 80 per cent of the 193 million people eligible to cast their votes. The death of almost about 290 polling workers and police officials from exhaustion from the world's largest one-day election has triggered calls for separating the vote in 2024.

Mr Joko's Indonesian Democratic Party of Struggle, or PDI-P, Golkar and Mr Prabowo's Gerindra Party led the vote tally in the elections to the nation's Lower House of Parliament, known as DPR, commission data showed on Monday (April 29).