Jakarta governor Ahok questioned after violent hardline demo

Friday's demonstration started peacefully but descended into chaos as night fell with protesters torching police cars and hurling rocks and bottles in the heart of the capital, as they demanded the leader be jailed for blasphemy.

Scores of police officers were injured and one man died amid the clashes close to the presidential palace, reportedly after tear gas fired by authorities triggered an asthma attack.

The protest involving tens of thousands of hardliners was sparked by accusations governor Basuki Tjahaja Purnama, a Christian and a member of Indonesia's ethnic Chinese minority, insulted the Koran during campaigning for elections for the Jakarta governorship.

He said his opponents were using a Koranic verse which suggests Muslims should not choose non-Muslims as leaders in order to trick people into voting against him.

Police had already launched the investigation into Purnama, known by his nickname Ahok, before Friday's protest after Muslim groups accused him of breaking the country's tough blasphemy laws.

On Monday the governor headed through a media scrum as he arrived at Jakarta police headquarters to be questioned as a witness in the case.

If found guilty Purnama -- who is favourite to win the February elections against two Muslim opponents -- could be jailed for up to five years.

However he is yet to be named a suspect in the case, a step which would mean authorities are considering filing charges.

Spokesman Agus Rianto pledged that police would conduct a fair investigation and people should not "doubt our neutrality", adding: "We will show the public our professionalism."

Purnama has apologised for his remarks, claiming that he was criticising his political rivals who were using the verse rather than the Koran itself. But this has done little to appease his opponents.

Thousands of police and soldiers were deployed before the rally in the capital of the world's most populous Muslim-majority nation, but it still took officers hours to quell the violence with tear gas and water cannons.