JAKARTA: Radicalism has spread to almost all provinces in Indonesia and the country's military is beefing up security in its Sulawesi border area amid the ongoing siege in the southern Philippine city of Marawi, the Indonesian military (TNI) said.

"Almost in all Indonesian provinces, except for Papua, there are IS sleeper cells," TNI chief General Gatot Nurmantyo said in a speech during a forum attended by media chiefs on Monday night.

Members of sleeper cells have been radicalised but remain inactive. They may resort to action when there is a trigger, the military warned.

Army major general Ganip Warsito, a territorial military commander overseeing Sulawesi and the border with the Philippines, said such citizens may be open to harbouring any escaping IS fighters from the Philippines if any of them ever managed to cross over to Indonesia.

General Ganip told reporters that security has been stepped up in anticipation of either the Philippines military clinching victory against the local militants or losing the battle in Marawi.

"If the Philippines wins, Indonesia would get a spill-over effect from the retreating militants, but if the Philippines loses, Mindanao would be a strong regional IS base that threatens Indonesia among others," he said.

This has prompted the Indonesian military to set up more military bases, locally known as Kodim, in the outlying areas on the border, he added.

Gen Ganip said intelligence and territorial defence operations around the border with the Philippines has not given any indication of any militant having 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 deemed to have the potential to be used in escape routes.

"All islands that are potential targets for infiltration, we have sent troops there. Those islands include Matutuang and Kawio," Gen Ganip said.

But since the border areas with the Philippines are traditional trading routes, escaping militants may attempt to cross over to Indonesia with the help of rogue merchants. Gen Ganip said the military is working to prevent this from happening. – The Straits Times