JAKARTA (Reuters) - Indonesian Muslims led by hardline groups plan to march to the presidential palace in the capital Jakarta on Friday, calling for the city’s Christian governor to be sacked for suspected blasphemy.

Jakarta's governor Basuki Tjahaja Purnama talks to his lawyers inside the court room during his trial at the North Jakarta District Court in Jakarta, Indonesia, December 27, 2016. REUTERS/Bagus Indahono/Pool

Religious and political tensions have been running high ahead of a second and final round of the Jakarta governor election on April 19. Incumbent Basuki Tjahaja Purnama, who is on trial for blasphemy, is running against a Muslim candidate.

The rally is expected to be the biggest demonstration since mass prayers in the grand mosque just days before the election’s first round on Feb. 15, and the latest in a series of protests that have tested religious and ethnic tolerance in the world’s largest Muslim-majority nation.

“An estimated 20,000 people from various groups, including students, will participate,” said national police spokesman Boy Rafli Amar.

“They will gather at the Istiqlal mosque (grand mosque) and the plan is to march to the presidential palace.”

Many Muslims in the city of more than 10 million believe Purnama, Jakarta’s first Christian and ethnic Chinese governor, insulted Islam when he made comments last year about his opponents’ use of the Koran in political campaigning.

Hundreds of thousands of Muslims took part in a series of rallies in Jakarta late last year and Purnama was put on trial for blasphemy. He has apologized for his comments but denied wrongdoing.

“We ask the government to imprison Ahok soon and relieve him of his official duties,” said Novel Bakmukmin, a member of the hardline Islamic Defenders Front, using Purnama’s popular nickname.

“This is not just about the Jakarta election any more. We want people who commit blasphemy against religion to be dealt with firmly.”

Purnama remains popular for his efforts to cut red tape and ease Jakarta’s chronic traffic congestion and flooding, but he faces a tight race with his rival, Anies Baswedan, a former education minister.

Purnama secured 43 percent of the vote in the first round in February and Baswedan got 40 percent. A candidate needs a simple majority to win the run-off election on April 19.

Most Indonesian Muslims adhere to moderate Sunni beliefs, and the country recognizes six religions including Hinduism, Catholicism and Buddhism, but minorities, even within Islam, have faced rising intolerance in recent years.