Radicalism has spread to almost all provinces in Indonesia and the country's military is beefing up security in the Sulawesi border area amid a siege in the southern Philippine city of Marawi, said the Indonesian military (TNI).
"Almost in all Indonesian provinces, except for Papua, there are ISIS sleeper cells," TNI chief Gatot Nurmantyo said in a forum on Monday, referring to the Islamic State in Iraq and Syria (ISIS).
The military warned that members of these sleeper cells are inactive now but may resort to action when triggered.
Army Major-General Ganip Warsito, a territorial military commander overseeing Sulawesi and the border with the Philippines, said such citizens may harbour ISIS fighters from the Philippines if any crossed over to Indonesia.
Maj-Gen Ganip told reporters security has been stepped up, whatever the outcome of the siege in Marawi, located in Mindanao.
"If the Philippines wins, Indonesia would get a spillover effect from the retreating militants. But if the Philippines loses, Mindanao would be a strong regional ISIS base that threatens Indonesia among others," he said.
This has led the Indonesian military to set up more military bases, locally known as Kodim, in the outlying areas on the border, he added.
Maj-Gen Ganip said intelligence and territorial defence operations around the border with the Philippines have not given any indication that any militant had crossed over and that the Indonesian military is striving to keep it that way.
Indonesian troops were previously stationed in only three islands on the border with the Philippines. As part of the stepped-up security, reinforcement was sent to all other islands in the area, which may be used in escape routes.
Militants who have gone to the southern Philippines to fight along the ISIS came from Indonesia, Malaysia and outside Asia.
Indonesian National Counter-terrorism Agency chief Suhardi Alius said last Thursday 40 Indonesians fighting in Marawi are followers of Jemaah Ansharut Daulah (JAD).
An offshoot of the Jemaah Islamiyah (JI) terror network which was behind the 2002 Bali bombings, JAD is known for mounting deadly attacks, especially on the Indonesian police.
JAD is led by Aman Abdurrahman, a jailed ideologue who ordered his followers to mount a suicide attack in Jakarta in January last year. It is also linked to other attacks in Indonesia, including twin suicide bombings in East Jakarta on May 23, which killed three policemen.
The authorities in Malaysia are also keeping a close watch on the sea borders between Sabah and southern Philippines, The Star reported yesterday.
Eastern Sabah Security Command chief Wan Abdul Bari Wan Abdul Khalid said security forces had been on heightened alert after militants took over parts of Marawi on May 26. "We are monitoring what's happening in Marawi on a day-by-day basis to see if there is any possible spillover," he said.
Meanwhile, the United States State Department has declared Majelis Mujahidin Indonesia (MMI) and Marwan Ibrahim Hussayn Tah al-Azawi, an Iraqi ISIS leader, as specially designated global terrorists.
It has prohibited US citizens from transactions or dealings with these designated terrorists, whose property and property interests in the US have all been frozen.
Set up in 2000 by JI founder Abu Bakar Bashir, the Al-Qaeda-linked MMI conducted attacks in Indonesia, including a May 2012 attack at a Canadian author's book launch in Jakarta. Marwan is linked to ISIS' development of chemical weapons for use in an ongoing battle against Iraqi security forces.