Indonesians to vote in regional elections, all eyes on Jakarta

Polls will open first in the east of the sprawling archipelago. In all, 101 elections will be held in the world's third-most populous democracy, for provincial, city and district chiefs.

In Jakarta, where the job of governor can be a springboard to the presidency, three candidates are competing: the Christian, ethnic Chinese incumbent, Basuki Tjahaja Purnama, and two Muslim candidates.

Mudslinging, political intrigue and rising hardline Islamist sentiment have overshadowed the Jakarta campaign, and raised questions about the role of religion in politics.

Indonesia has the world's largest Muslim population but it enshrines religious diversity in an officially secular system.

Purnama, or Ahok as he is commonly known, is on trial on a charge of insulting the Koran, a case that has brought thousands of Muslims onto the streets, urging voters to shun a non-Muslim as leader.

He denies the charge and has been faring well in opinion polls, which analysts attribute to his record of improving the bureaucracy and taking steps to ease horrendous traffic jams and flooding.

His rivals are Agus Yudhoyono, a son of former president Susilo Bambang Yudhoyono, and former education minister Anies Baswedan.

Purnama was a deputy to President Joko Widodo when he was the previous Jakarta governor and Widodo's party is backing him.

Baswedan is backed by a former general who Widodo beat in the last presidential election in 2014, Prabowo Subianto, who is promising a comeback to the national stage.

The Jakarta vote is being widely seen as a proxy battle for the next presidential election, due in 2019.

The competition has been particularly bitter between Purnama's camp and that of Yudhoyono. Former president Yudhoyono said on Twitter on Tuesday that various figures were trying to sabotage his son's chances.

Police will deploy 75,000 personnel across the country with 16,000 on duty in Jakarta, where concern lingers over the possibility of hardline Muslim groups taking to the streets to agitate against Purnama.

Some Islamist groups have said they will send members to polling stations to "safeguard" the vote.

"We will send trained volunteers to at least 13,000 polling stations to watch as the votes are counted," said Muhammad al Khaththath of the Islamic People's Forum, which was among the organisers of the anti-Purnama rallies.

"We are sure that in this situation, a Muslim will win," he said.

Polling stations will close by 0600 GMT. Quick counts, expected shortly after, are tallies of votes by private polling firms at a sample of voting booths across the city.

The General Elections Commission is expected to announce official results after about two weeks.