
The triple suicide bombings targeting churches in the Indonesian city of Surabaya in mid-May focused global attention on the explosive tactics of Islamic State-linked militant groups in Southeast Asia. Yet while the scale of the attacks in Surabaya sent shockwaves through the region, 1,500 kilometers to the northeast on the Philippines’ insurgency-plagued southern island of Mindanao, IED (improvised explosive device) attacks by Islamist groups have risen steadily since the end of the Marawi siege last October.

The bombing of a cathedral in Koronadal city injured three people in late April, while an explosion in a crowded bar in Jolo left another 10 civilians wounded in early-May. These IED attacks were among the latest aimed at harming civilians in the region. The first was carried out by the Bangsamoro Islamic Freedom Fighters (BIFF) while the second occurred in a stronghold of the notorious Abu Sayyaf group.

Yet more often security forces have been the preferred target of IED blasts, launched with increased regularity not only by Islamist groups but also the communist rebels of the New People’s Army (NPA). With Mindanao under an extended period of Martial Law – which was first imposed by President Rodrigo Duterte at the height of the five-month Marawi siege – the long-troubled island’s plethora of armed groups appear to be turning to IEDs as they come under sustained pressure from military operations.

The use of IEDs is nothing new in the southern Philippines, which has a history of large-scale militant bombings. However, in the current context, an influx of foreign fighters trained in bomb-making has been amplified by insurgent groups shifting to more covert, guerrilla-style tactics in response to the ongoing crackdown by government forces in Mindanao, resulting in a surge in small-scale IED attacks.

To what extent are IEDs becoming a weapon of choice in Mindanao’s multiple insurgencies? And what is being done to mitigate the growing threat from these makeshift devices before it escalates further?

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Rising IED Attacks in Mindanao Since the Marawi Siege

The use of IEDs was a key tactic employed by the ISIS-aligned Maute group as they laid siege to Marawi from May to October last year, and this trend has continued across Mindanao since the jihadist uprising was extinguished by the Philippine military. According to data obtained through local media reports, the final three months of 2017 witnessed 10 attempted IED attacks by armed groups in the region. Nine of the devices detonated, resulting in four deaths and 30 injuries. In the first three months of 2018 the number of attempted attacks almost doubled to 19, with 15 of the devices exploding as intended, killing another four people and leaving 25 wounded. So far, the trend has continued during April and May, with another 16 attempted attacks since the beginning of April maiming at least 24 people. Three groups – Abu Sayyaf, the BIFF, and the NPA – are mostly responsible.

The threat varies geographically across the island. In western provinces of Mindanao, the ISIS-aligned militants of the BIFF have carried-out the majority of IED attacks – 31 since the beginning of October. In some of the larger attacks attributed to the BIFF, on December 8 three devices exploded in separate locations across Maguindanao province, wounding a police officer and seven soldiers; while on New Year’s Eve a bomb exploded onboard a motorcycle near the entrance to a packed bar in Tacurong city, killing two civilians and leaving another 16 wounded. The region’s longer-established Islamist militants of Abu Sayyaf have also carried out IED attacks in the western maritime provinces of Basilan and Sulu.


In eastern Mindanao, the IED threat emanates primarily from the Maoist rebels of the NPA, who have waged a long-running insurgency against the government since 1969. The group has used IEDs on seven occasions so far in Mindanao this year. Whereas Abu Sayyaf and the BIFF often target civilians, the NPA uses explosive devices to ambush security patrols. In late February an IED blast killed a soldier and left two others wounded near Davao, while on March 20 three soldiers were injured after the rebels used a roadside IED to blow up a military truck in Compostela Valley. In early March the army discovered a cache of bomb-making materials in Bukidnon and later announced the seizure of 174 IEDs from the group during the first two months of 2018, evidencing the growing scale of the threat.

What explains the increasing number of IED attacks launched by armed groups in Mindanao?

An important first point to note – as mentioned earlier– is that IED attacks are not a new phenomenon in the Philippines. The country has previously been rocked by several mass-casualty attacks involving explosives, most notoriously when Abu Sayyaf bombed a passenger ferry in Manila Bay in February 2004, killing 116 people. More recently, Islamist militants bombed a busy night market in Davao city in September 2016, killing 15 and leaving more than 70 wounded. In addition to large-scale, attention-grabbing attacks targeting civilians, militant groups in the conflict-affected south – in particular Abu Sayyaf – have a history of using IEDs against the security forces. The problem was exacerbated by the influx of al-Qaeda- and Jemaah Islamiyah-affiliated militants trained in bomb-making skills during the 1990s, such as Indonesian jihadist Rahman al-Ghozi and the Malaysian expert bomb-maker, Marwan.

Influx of Foreign Fighters and the Transfer of Bomb-Making Skills

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The present wave of IED attacks by Islamist groups in Mindanao can be attributed to a repeat scenario, after recent years witnessed a second influx of foreign fighters with bomb-making skills to the island from neighboring Indonesia. However, this time the wave of recruits was inspired by the modern-day successor to al-Qaeda as the leader of transnational jihadism: ISIS. As a result of the large influx of militants before the Marawi siege, IED-making skills have been transferred from fighters in the Middle East and jihadi hotspots in Southeast Asia to local militants in the maritime borderlands of the southern Philippines. Foreign fighters who joined up with the Mautes are thought to have trained members of the BIFF, which is now Islamic State’s primary vanguard in the region and poses the main IED threat.

The influx of ISIS-trained bomb-makers prior to the Marawi siege was facilitated by lax security in the porous waterways surrounding Mindanao. Jihadists were able to amass in a region already blighted by a climate of lawlessness, the presence of armed groups, and a well-developed illicit economy. These conditions fostered an ideal environment for the transfer of militants, IED components, and bomb-making skills. ISIS was likely able to further exploit these vulnerabilities by using encrypted messaging apps to disseminate bomb-making knowledge hidden from the scrutiny of law enforcement agencies.

In January, the Philippine army’s intelligence chief, Maj. Gen. Fernando Trinidad, confirmed that foreign fighters remained present in Mindanao. He said these foreign fighters had trained local militants in urban warfare and the construction of IEDs. Yet such fears had already been realized last October during the final throes of the Marawi siege, when government soldiers discovered a Maute-run IED manufacturing base, indicating the extent of militant training and the mass production of IEDs on an industrial scale.

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A year since the militant uprising in Marawi began, the ongoing military crackdown in Mindanao is providing ample opportunity for Islamic State’s remnants to put their newly acquired skills to the test. Pushed onto the back foot by Martial Law, groups such as Abu Sayyaf, the BIFF, and the NPA have been forced to splinter and adopt guerrilla-like tactics to an even greater extent than was already the case. Having sustained heavy losses on the battlefield and with their capability to engage in conventional ground battles against a bolstered military gradually receding, IED attacks serve as a way for increasingly desperate armed groups to make their presence felt and demonstrate that they are still alive.

How Can the Growing IED Threat Be Countered?

For the government, countering the IED threat remains a huge challenge. Local intelligence reports can help prevent a planned attack from succeeding when a device is spotted before it explodes. Since October, military bomb-disposal experts have thwarted attempted attacks after responding to call-outs and defusing or safely detonating primed devices on at least 10 occasions. The military has also seized several caches of bomb-making materials during raids on insurgent hideouts across the island.


At a wider regional level, authorities have implemented measures intended to subvert the underlying conditions enabling the transport of foreign fighters and IED components in porous maritime border areas. Since last June, Indonesia, Malaysia, and the Philippines have conducted trilateral naval and air patrols over the Sulu Sea to detect and disrupt suspicious activities, including the smuggling of arms and bomb-making materials. Just a few weeks ago Malaysian soldiers arrested a man onboard a vessel found to be containing 10,000 detonator fuses, headed in the rough direction of Mindanao’s coastline.

These cooperative measures signal hope for the future. Yet the present IED threat will remain hard to mitigate and effective countermeasures difficult to implement for as long as Mindanao’s current generation of militants are able to retain and pass on their bomb-making knowledge to new recruits.

As Philippine troops continue their dual crackdown on Mindanao’s Islamist militants and communist rebels under Duterte, for the regions’ armed groups – increasingly on the retreat – IEDs are becoming a weapon of choice. As the conflicts raging in Mindanao become more asymmetric, the use of IEDs enables militants to inflict damage on the military and strike fear into communities, without incurring casualties of their own in the struggle to maintain influence and hold on to small pockets of territory.

IEDs are a particularly potent weapon in the rural jungle environments of Mindanao, where armed groups have for decades sought new means to demonstrate their survival and make their presence felt. Yet IEDs also increasingly pose a threat in urban settings such as Marawi, where the laying of IEDs became a key factor in extending the length of the siege as the Maute group became entrenched in their positions. The Philippine army has repeatedly warned of large-scale Islamist assaults using IEDs on other major cities in the region, with Davao, Cotabato, and Zamboanga mooted as potential targets.

While a repeat Marawi-type scenario can’t be ruled out, there also remains a possibility of large-scale bomb attacks similar to those seen in Indonesia. Even if these two worst-case scenarios are avoided, the proliferation of IEDs in the region remains a major concern and will further complicate the ongoing efforts of the military to extinguish Mindanao’s intractable – and increasingly explosive – insurgencies.

Michael Hart is a freelance writer and researcher focusing on civil conflict and terrorism in Southeast Asia.