By Agustinus Beo Da Costa and Kanupriya Kapoor
JAKARTA (Reuters) - Indonesians began voting on Wednesday in local elections across the sprawling archipelago, after a bitterly fought campaign to win the prize of governing the capital, Jakarta, that has inflamed religious tensions in the Muslim-majority nation.
Polls opened first in Papua province in the east, before voting kicked off in Jakarta several hours later. In all, 101 elections are being held in the world's third-most populous democracy, for provincial, city and district chiefs.
The biggest focus is on 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 his support has rebounded to lead many opinion polls, which analysts attribute to his record of improving the bureaucracy and taking steps to ease congestion and flooding.
A scrum of reporters waited near a polling station, set up under white marquee tents, in North Jakarta for Purnama to vote.
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 are deploying 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 pledged to 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 organizers 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.
If no candidate achieves a majority in the first round in any provincial vote, including Jakarta, a runoff is expected between the two candidates securing the most votes.
(Writing by Ed Davies; Editing by Robert Birsel and Michael Perry)