The Christian governor of Jakarta, Basuki "Ahok" Tjahaja Purnama, and his Muslim opponent are neck and neck in the race to lead Indonesia's capital, an opinion poll showed on Wednesday, a week ahead of the hard fought vote.

The election campaign - which has been among the most divisive in the city's history - has been marred by religious and ethnic tension over the blasphemy trial of the incumbent Purnama, who is accused of insulting Islam.

Purnama was on 46.9 percent of the sample vote, trailing his rival Anies Baswedan by 1 percentage point in one of the first opinion polls published since the two candidates made it through a first round election in mid-February.

A candidate needs a simple majority to win.

Pollster Saiful Mujani Research Center (SMRC) said the survey of 800 respondents showed Baswedan enjoyed support primarily because of his Islamic faith, while Purnama was popular due to his record in office.

Nearly 90 percent of Indonesia's 250 million population is Muslim, but the country recognizes six religions and is home to sizeable communities of Christians, Hindus and those adhering to traditional beliefs.

The state ideology, Pancasila, enshrines religious diversity in an officially secular system.

Purnama, who is Jakarta's first ethnic Chinese and Christian governor, offended Muslim groups when he made comments last year about his opponents' use of the Islamic holy book, the Koran, in political campaigning.

Since then, Muslims, led by hardline groups, have held mass rallies to call for Purnama to be sacked, and to urge voters not to elect a non-Muslim. The rallies have raised concerns about growing religious intolerance in the world's largest Muslim-majority nation.

Purnama has apologised for his comments and denied any wrongdoing. He faces up to four years in prison if found guilty.

Judges hearing the case decided this week to adjourn the trial until after voting day, after police and prosecutors asked for a delay because of security concerns.