The man was detained in a raid on his house outside the capital Jakarta yesterday during which an IS flag, ammunition, and 16 weapons were discovered, mostly handguns and modified air rifles, according to Aswin Siregar, spokesman for Indonesia’s Densus 88 counter-terrorism taskforce.

The suspect, an employee with a state railway company, told authorities of his plan to attack the police facility, but gave no time frame or motive, Aswin said.

He added that the suspect, once a member of a defunct militant organisation, had posted pro-IS content on social media and sought to raise funds for extremism via the Telegram messaging app.

“We were shocked by the evidence we found,” Aswin told a news conference.

“The movement of ISIS or supporters of ISIS…has never stopped even when it’s not visible to our eyes that they congregate,” he said, referring to the IS.

Todd Elliott, a security analyst at Concorde Consulting, said “the arrest of the suspect after a relatively low in terrorist activity since the start of 2023 highlights the lingering existence of a small but highly radical minority in the country.”

Indonesia, the world’s largest Muslim-majority nation, suffered its worst militant attack in 2002 when two nightclubs on the island of Bali were bombed, killing 202 people, mostly foreign tourists.

Analysts say the threat of extremist attacks has since diminished significantly and while arrests of suspected extremists do take place, pledges of allegiance to the IS have been rare.