Voters in Jakarta are choosing a governor in a run-off election that has been called “the dirtiest and most divisive” Indonesia has ever seen.
Polls suggest it is a close race between incumbent Basuki Tjahaja Purnama, a Christian of Chinese descent, and Anies Rasyid Baswedan, a Muslim. Mr. Purnama is also on trial for blasphemy, which he denies.
Security is tight amid heightened racial and religious tensions.
Hard-line Islamist groups have accused Mr. Purnama of insulting a Koranic verse during a campaign speech and have rallied large crowds against him.
Correspondents say this has made the election a choice between secularism and a growing hard-line Islamist movement in Indonesia.
Reports say though extra security officers have been deployed to polling stations, the mood in Jakarta is not overly tense and there is still a festive atmosphere.
Mr. Purnama, also popularly known as “Ahok”, voted with his family in north Jakarta early on Wednesday morning.
He told reporters: “Jakartans must use their voice as the future of Jakarta is in their hands. Don’t be afraid, the police are here providing security.”
A coalition of hardline Islamic groups supporting Mr. Basedan previously said that it would send at least 100 activists to each polling station to monitor voting. But correspondents say they have a very limited presence so far.
Police have warned against voter intimidation.
Rizieq Shihab, leader of the Islamic Defenders Front which has been leading protests against Mr. Purnama, has also cast his vote.
The election has also seen anti-Chinese sentiment, sparking unease in a country that has seen violence against its Chinese minority previously.
A number of Chinese Indonesians who turned up to vote told reporters that they were not intimidated.