The election race for the governor of Indonesia's capital, Jakarta, looks set to go to a second round after no candidate secured 50% of votes.
Unofficial counts show incumbent Basuki Tjahaja Purnama, or "Ahok", a Christian seen as the front-runner until he went on trial for insulting Islam, took 43%.
His closest rival, Islamic conservative Anies Rasyid Baswedan, was close behind him with 40%.
The result of the run-off will likely hinge on the third-candidate voters.
Agus Harimurti Yudhoyono, also a Muslim, trailed with about 17%. If his supporters choose to vote along religious grounds, it could benefit Mr Baswedan, but this is by no means certain.
Full official results are not expected until the end of the month, with the next vote expected to take place on 19 April.
Wednesday's election - one of hundreds of regional ballots taking place across the country - exposed sharp religious and social divisions, overshadowing the many pressing social issues facing the capital.
Mr Purnama, or "Ahok", is the first Christian and minority ethnic Chinese leader of Jakarta in over 50 years. He stepped into the role from the deputy post without election in 2014, when his predecessor, Joko "Jokowi" Widodo became president.
Ahok, who has the backing of the president, was largely popular with Jakarta residents for his efforts to tackle corruption, traffic and vice, and to improve education and healthcare.
But last year huge and sometimes violent protests erupted, led by hardline Islamists, after he told some of his supporters not to be misled by religious leaders who said the Koran forbade them from voting for a non-Muslim.
He went on trial in late December, and denied blasphemy, saying his comments were aimed at politicians "incorrectly" using the Koran against him. If convicted, he faces a maximum five-year jail sentence, though could still govern while appeals are heard.
As results came in he told his supporters, many wearing his signature checked shirt, that it was "not over yet".
Mr Baswedan has made appeals to conservative Muslim voters, though has denied exploiting race and religion as an issue.
His party said he had listened to the concerns of voters, including people evicted during Mr Purnama's operations to clean-up slum areas, Reuters reports.
Indonesia is the world's most populous Muslim nation. About 85% of the population are Muslim, but the country officially respects six religions.
Watching closely; Rebecca Henshke, BBC News, Jakarta
This sprawling mega city woke up this morning bracing itself for two more months of an election campaign that has been divisive and dirty.
Most observers are warning that any run-off between Governor Purnama and Anis Baswedan could inflame religious tensions further.
At a polling station in Central Jakarta on Wednesday, each time a vote for Mr Baswedan was counted his supporters there cried out "Allahu Akbar" or "God is greatest". He has actively courted the conservative Muslim vote.
But his campaign manager insists that Anis Baswedan, like most Indonesians, is tolerant and has great respect for the country's founding principles of "unity in diversity".
"In an election campaign you need to bring everyone together and reach out to all groups. Governor Purnama is the one who made religion an issue, not us. He is one who started this."
Everyone here is watching closely to see who will finish it.