Indonesian security forces are strengthening the archipelagic country’s northern border, fearing that Islamic State (IS) fighters still clinging to parts of the besieged southern Philippine city of Marawi may inspire similar bold terror actions in their territory.

Indonesian Defense Minister Ryamizard Ricacudu met with his neighboring counterparts on the Northern Kalimantan island of Tarakan last week to coordinate a response to what terrorism expert Sidney Jones calls a “game-changer” in the struggle to contain a growing regional threat.

More than 300 combatants and civilians have died since the IS-linked Maute Group and militants loyal to Abu Sayyaf Group leader Isnilon Hapilon, IS’ anointed leader in the Philippines, took over the Lanao del Sur provincial capital on May 23, a move that led President Rodrigo Duterte to declare martial law over the southern island of Mindanao.

Brothers Omarkhayam and Abdullah Maute, the IS affiliate group’s leaders, grew up in Marawi, but spent years studying in Jordan and Egypt where Omarkhayam met and married an Indonesian student whose father runs a conservative Islamic boarding house in the eastern suburbs of Jakarta.

Five other Maute brothers are believed to have joined the battle, but one was captured at a military checkpoint near the northern city of Cagayan de Oro, where the Maute Group first announced its presence in a nightclub bombing in 2013. The fighting has resulted in an estimated over 400 deaths and massive civilian displacement.

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Still, it is hard to imagine anything on the scale of Marawi happening in Indonesia. Unlike lawless Mindanao, which is awash in modern weaponry due to decades of insurgency, Indonesian militants have limited access to the sort of firearms and ammunition stocks that have allowed the Maute militants to hold out for so long.

Indonesia’s military and police are believed to have done a good job so far in preventing substantial arms supplies crossing the porous Sulu Sea into the border provinces of North and East Kalimantan and North and Central Sulawesi.

Over the past two years, troops and paramilitary police have also effectively crushed Indonesia’s only active Islamic insurgency in the jungles of Central Sulawesi, killing Mujahidin Indonesia Timur leader Santoso and scattering the rest of his small band.

Marawi has sent alarm bells ringing across the region, in large part because it was never anticipated and caught Duterte – the country’s first Mindanao-born president — and his strong-handed administration completely off guard.

Philippine Marines stand guard outside a mosque in Marawi City in southern Philippines May 30, 2017. REUTERS/Erik De Castro - RTX386BF
Philippine Marines stand guard outside a mosque in Marawi City in southern Philippines May 30, 2017. Photo: Reuters/Erik De Castro

It was initially hoped Duterte would make progress in forging peace deals with the Moro Islamic Liberation Front (MILF) and the recalcitrant Communist Party of Philippines (CPP), but his conciliatory efforts so far have failed to stop the violence.

His federalism policy, aimed at giving more autonomy to local governments, has also gone nowhere. The Abu Sayyaf Group, a brutal kidnap-for-ransom gang that has claimed loyalty to IS, predictably answered his peace overtures with kidnappings and the beheading of hostages.

In the meantime, his government and the military intelligence appear to have totally misjudged the rise of the Maute Group, which gave a hint of things to come last November by briefly occupying the town of Butig (pop: 17,000) at the southern end of Lake Lanao.

Marawi represents Duterte’s greatest security challenge, a reminder of the 1974 Battle of Jolo waged between government and Moro National Liberation Front (MNLF) forces on the southern Philippine island of Sulu, which left the town in ruins and thousands dead.

A view of the Maute group stronghold with an ISIS flag in Marawi City in southern Philippines May 29, 2017. REUTERS/Erik De Castro
A view of the Maute group stronghold with an Islamic State flag in Marawi City in southern Philippines May 29, 2017. Photo: Reuters/Erik De Castro

Noting the way the Marawi siege has brought together militants from the Philippines, Malaysia and Indonesia, Jones told a recent American Chamber of Commerce in Indonesia briefing: “Marawi is a game changer and now the preferred jihadist destination is next door.”

About 20 to 40 Indonesian fighters are believed to have been involved in the fighting, most of them from the pro-IS Jamaah Ansharut Daulah (JAD), the same Indonesian group which staged the January 2016 bomb and gun attack in downtown Jakarta.

Jones says more are likely to join the Maute Group’s stated cause of creating a Southeast Asian caliphate now that the IS strongholds of Mosul and Raqaa in Iraq and Syria have been largely cut off by government forces.

Several other foiled terrorist plots since the Jakarta attack have been blamed on either JAD — and its jailed leader Aman Abdurahman – or Bahun Naim, a 33-year-old computer technician who took his wife and two children with him when he travelled to Syria to join IS in 2014.

Indonesian anti-terror police from Detachment 88 stand guard near explosive materials and other evidence confiscated in raids on suspected militants during a media briefing at police headquarters in Jakarta, Indonesia, November 30, 2016. Picture taken November 30, 2016. REUTERS/Beawiharta - RTX2WABJ
Indonesian anti-terror police  stand near explosive materials confiscated in raids on suspected terrorists at police headquarters in Jakarta, Indonesia, November 30, 2016. Photo: Reuters/Beawiharta

In the Jakarta assault, the seven gunmen carried explosive backpacks and were only armed with pistols, an indication they did not have access to the assault rifles that would add a whole new dimension to the terrorist threat in Indonesia.

In Marawi, the militants holed up in basements and tunnels are armed with everything from rocket grenades and heavy machine guns to .50 calibre sniper rifles and a seemingly inexhaustible supply of ammunition, which may have been have been stockpiled in preparation for the takeover.

Fearful that some of those weapons might end up in Indonesia, the Philippines, Malaysia and Indonesia last week began unprecedented joint naval patrols in the Sulu Sea, both to counter arms-smuggling and put a stop to Abu Sayyaf Group attacks on commercial shipping.

Whether those patrols are able to stem the rising terrorism threat in the region, however, is yet to be seen.