Police on Friday fired tear-gas at protestors who were trying to meet Joko to demand the prosecution of Jakarta governor Basuki Tjahaja Purnama – better known by his Chinese nickname “Ahok” – for remark she made in September which some Muslims considered to be blasphemous.

“We regret the event at night when the protestors should have disbanded but instead turned to rioting,” Joko said. “We see that(the protest) has been exploited by political actors seeking to take advantage of the situation.”

One person died from an asthma attack following the clashes,which broke out at night after most of the estimated 100,000demonstrators left peacefully, police said.

Joko urged the public to remain calm and said that the case involving Purnama, a key ally, would be investigated promptly and transparently.

In a video circulating on the internet last month, Purnama said his opponents in next year’s gubernatorial election had used a verse from the Koran to deceive voters and prevent him from winning another term.

Many Muslims in Indonesia interpret the text in question as prohibiting them from electing non-Muslims as their leaders.

Purnama became Jakarta’s first ethnically-Chinese governor when he took over from Joko in 2014.

Backed by Joko’s Indonesian Democratic Party of Struggle, he is seeking another term in the election scheduled for February 15.

Purnama has apologized for the Koran remarks, but his expression of remorse failed to appease hardline Muslims.

Blasphemy is defined in Indonesia as “publicly expressing hostility to, misusing or disparaging any of the recognized religions” and is punishable by up to five years in prison.