After a campaign marked by sectarian and ethnic tensions, voting has begun in the second round of Jakarta's election for a new governor.

The vote for Indonesian capital's governor pits Basuki "Ahok" Tjahaja Purnama, the city's first Christian and ethnic Chinese leader, against former education minister Anies Baswedan, who has courted the support of conservative Muslims despite his liberal credentials.

Recent polls suggest that the race is too close to call, with Baswedan leading by a percentage point in two surveys.

Official results will not be announced until the first week of May, but quick counts by independent pollsters should be able to predict the winner hours after the polls close.

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Security is also unusually tight for the poll. Police say about 66,000 personnel will be deployed throughout the city of some 10 million people to prevent voter intimidation and civil unrest.

The election is viewed as a test for Indonesia’s young democracy and record of religious tolerance.

"During this campaign, not only politics and policies were being discussed - it was mostly a campaign about identity and religion," said Al Jazeera's Step Vaessan, reporting from Jakarta.

Blasphemy trial

In an attempt to lift turnout, political groups have called for Indonesians to travel to Jakarta from elsewhere.

Purnama's bid for a second term has been dogged by a blasphemy case triggered by comments he made on the Quran that were deemed insulting to Islam.

Purnama won a three-way first-round vote on February 15, securing 43 percent of the votes. Baswedan came second with 40 percent.

Purnama's remarks that there were people who deceived Muslim voters into believing that the Quran commands them not to vote for Jews and Christians sparked massive street protests by conservatives in November and December.

Purnama was charged with blasphemy and is facing a maximum five-year jail term if found guilty. He remains free and a verdict is expected after the election.

He has apologised for the remarks, and said that he was referring to those who misused religion for political gain.