Indonesian police said on Wednesday they will go ahead with an investigation into a blasphemy complaint brought by Muslim groups against the Christian and ethnic Chinese governor of Jakarta and banned him from leaving the country.

The decision to officially name Basuki Tjahaja Purnama a suspect comes amid simmering religious and ethnic tension and is likely to stoke concerns over rising hardliner Islamic sentiment in the world's largest Muslim-majority nation.

Ari Dono Sukmanto, chief of the National Police criminal investigation department, told reporters that “the dominant opinion is that this case should be settled in court”.

Some analysts said the decision was a blow to Indonesia's young democracy.

“It sets a bad precedent for minorities as the legal process can be dictated by public pressure,” said Irine Gayatri, political analyst at the Indonesian Institute of Sciences.

Indonesia recognises six religions and is home to several minority groups that adhere to traditional beliefs.

The blasphemy allegations centre on a speech Purnama made in September in which he said his opponents had deceived voters by attacking him using a verse from the Koran.

Purnama has denied blasphemy but apologised for the comments. Hardliner Muslim groups have demanded that he resign, claiming that he insulted Islam's holy book.

More than 100,000 Muslims marched against him this month, urging voters not to re-elect him in February.

“I accept the status of suspect and believe in the professionalism of the police,” Purnama told reporters after the decision.

“This is not just a case about me but about determining the direction this country is going in.”

Presidential spokesman Johan Budi called for all sides to respect the police decision. “From the beginning, the president has said he would not intervene,” Budi said.

Support for Purnama, a Protestant once hugely popular for his tough, reformist approach to running the city of 10 million people, has plummeted during the controversy, according to an opinion poll published last week.

A decision to drop the case could have sparked mass protests led by hardline Muslims against not just Purnama but also Widodo, who is seen as a key backer of the governor.