Indonesians are voting in a parliamentary election likely to be have a big influence on the country's presidential poll later this year.

Over 186 million people are registered to cast ballots in the Wednesday vote. About 30 percent of them are young people, many of whom are voting for the first time.

One voter, Sugito Waluyo, said he is optimistic about what the election represents.

"We will continue to become a mature democracy. This is the fifth free election we have had since 1998 and we hope that our representatives listen to the voice of the people."

The main opposition Democratic Party of Struggle is expected to dominate the election, making Jakarta governor Joko Widodo likely to become the country's next leader.

Widodo, known as "Jokowi," is popular for his reputation for transparency and his hands-on approach to governance. He spoke to reporters after voting in Jakarta early Wednesday.

"I hope this election will be held honestly, fairly, so that everyone can exercise their right to vote according to their will."

Opinion polls show President Susilo Bambang Yudhoyono's Democratic Party is not expected to fair well after a string of high-level corruption scandals.

Official results will be announced by May 9, but a quick count of the polls is expected within 24 hours. The presidential election is on July 9.

Wednesday's vote marks the fourth time Indonesians will democratically elect their parliament, since the collapse of former leader Suharto's 32-year authoritarian rule.