The recent arrests of 11 suspected terrorists by authorities in Indonesia underline how terrorism remains a persistent security challenge, with analysts warning that militant networks are communicating online through smaller and decentralised cells despite stronger enforcement.

The Indonesian National Police’s counterterrorism force, Special Detachment 88 (Densus 88), said on Sunday that 11 suspected terrorists had been arrested in raids across West Java, Central Java, Central Sulawesi, South Sulawesi, Riau and North Maluku provinces since its operations began on Friday.

“The suspects are believed to be affiliated with Daulah Islamiyah and other terrorist networks,” Densus 88 spokesman Mayndra Eka Wardhana said in a statement. Wardhana said that the suspects communicated with each other through “virtual rooms”.

“Early investigations indicate that the suspects from various regions were connected virtually. They utilised online meetings for indoctrination, training and network consolidation,” he said.

Daulah Islamiyah refers to radical Islamists whose goals are aligned with Islamic State (IS) ideology.

Several suspects allegedly took part in militancy training, such as physical and shooting drills, and other activities linked to preparations for terrorist acts, Wardhana said.

Densus 88 has also arrested other alleged terrorists earlier this year. In May, eight suspected terrorists linked to the IS-affiliated Jamaah Ansharut Daulah (JAD) network were arrested in Central Sulawesi. The suspects spread radical propaganda through social media posts, videos and other content.

Last year, Densus 88 arrested 51 suspected terrorists, a drop from the 196 arrested in 2024, according to data from the national police.

Asked by This Week in Asia about the estimated total of active members and supporters of Daulah Islamiyah in Indonesia, Wardhana said that he could not reveal the number due to it being “excluded information”. He also declined to mention the force’s strategy to detect the terrorist cells’ online groups.

The recent operations highlight how extremist ideology continues to sprout in smaller, decentralised and harder-to-detect cells two years after the landmark dissolution of Jemaah Islamiah (JI). “From 2023 to 2025, we can indeed say there were zero terror attacks [in Indonesia], but the terrorist networks are always there,” said Chaula Rininta Anindya, an assistant professor of international relations at the University of Indonesia.

“The extent of the terrorist networks that form online is difficult to detect. The chat groups are usually numerous. Their development is rapid, while communication platforms are becoming more varied. We don’t know what tools they use to support their discourse.”Radical mindsets – “based on religion or nihilistic violent extremism” – also posed a problem in other Southeast Asian countries, such as Singapore and the Philippines, Chaula said.

In July, three Singaporean teenagers aged between 14 and 19 were arrested after they were allegedly self-radicalised by violent extremist ideologues and planned to carry out separate attacks, Singapore’s Internal Security Department said.

According to Chaula, the drop in overall attack statistics in Indonesia is made possible due to its stronger legal framework on counterterrorism. In May, the government issued a presidential decree to eradicate terrorism through national preparedness and counter-radicalisation.

Under a 2018 law on terrorism, law enforcement is authorised to arrest suspected terrorists pre-emptively without having to wait for their planned actions to be carried out.

In June 2024, leaders of JI disbanded the group, which was responsible for multiple bombing attacks in Indonesia in the early 2000s. However, not all members of JI “agreed to rejoin the Indonesian republic”, according to Tegar Bimantoro, a criminologist with the Institute of Andi Sapada. Some of them might have formed cells to “consolidate” their networks and connected through digital platforms, he said.

Tegar warned that it would be “very dangerous” if a recidivist were to return to extremism or rejoin a terror cell.

“Someone who has been in prison already has access to materials on bomb-making, for example. It would be especially dangerous if they pass on their knowledge to their followers,” Tegar said.

A study on terrorist recidivism published by S. Rajaratnam School of International Studies in Singapore released on Friday estimated that 4 to 11 per cent of 1,200 former terrorists who had undergone a deradicalisation programme in Indonesia over the past decade subsequently reoffended.

In November, Densus 88 arrested five suspected terrorists for allegedly recruiting more than 110 children into terrorist networks via social media, online games and encrypted messaging since the end of 2024. One of the five suspects was a former prisoner affiliated with the JAD.

In April, Eddy Hartono, head of the National Counterterrorism Agency (BNPT), told reporters that a chat feature in one online game had been used as a “recruitment tool”, dubbing the practice as “digital grooming”.

Tegar said that sustained counterterrorism in Indonesia would depend not only on arrests but also on commitment to social reintegration and economic empowerment over the long term.

“When their economy is good and their basic needs are met, I think ideological concerns can be put on the back burner. The current phenomenon is that the economic well-being of these former terrorist convicts is still below standard,” Tegar said.

“Today, ideology should not be a main issue when discussing terrorist convicts. We need to talk about reintegration, how they can live sustainably.”Chaula urged Jakarta and BNPT to work together with local governments on additional oversight or social support for former convicts, who typically would return to their hometowns following their release from prisons.

“To ensure more effective or intensive monitoring, local governments must be involved. This includes ensuring former terrorist convicts’ reintegration into society, employment, or even simple support for their families, such as schooling for their children. These are things that will be easier to accomplish when local governments are involved,” she said.