JAKARTA (THE JAKARTA POST/ASIA NEWS NETWORK) - The police are investigating whether a bomb threat at City Hall is credible, as the country faces growing threats from domestic terrorists who support the Islamic State in Iraq and Syria (ISIS) movement.

"Yes, it is true that there was a bomb threat (at City Hall) at around 9.15am," Gambir Police head Ida Ketut Grahananta Krisna Rendra told The Jakarta Post on Wednesday (July 20).

Unusually, City Hall's security officers checked the bags of every visitor and employee arriving in the area on Wednesday morning. Hundreds of personnel from the Jakarta Police's Gegana bomb disposal squad were seen combing City Hall and other buildings in the vicinity such as the City Council's offices.

The bomb threat, apparently aimed at Jakarta Governor Basuki "Ahok" Tjahaja Purnama, came shortly after the National Police and the Indonesian Military killed pro-ISIS terrorist Santoso, leader of the East Indonesia Mujahidin (MIT) group.

The political rise of Ahok, the first Christian of Chinese descent to lead the country's capital, has been strongly opposed by hardliners in the Muslim-majority country.

A report by the Institute for Policy Analysis of Conflict (IPAC) mentioned that an Indonesian ISIS fighter in Syria, Bahrun Naim, ordered Arif Hidayatullah to assassinate Ahok in September 2015.

But Naim shifted his focus from Ahok to former National Counterterrorism Agency (BNPT) chief Tito Karnavian, Ahok's friend, who was recently installed as National Police chief.

Arif, also known as Abu Muzab, was arrested in 2015 for allegedly recruiting ISIS supporters to carry out attacks on Indonesian soil.

His recruits included Nur Rohman, a suicide bomber who attacked the Surakarta Police headquarters on the eve of Idul Fitri.