The militants who carried out Thursday's attack in Central Jakarta had made-in-the-Philippines firearms, while Indonesian police say they had received funding as well as operational instructions from Syria.
At least one was confirmed to have undergone paramilitary training at an extremist camp run by the now disbanded Jemaah Islamiah (JI) in Aceh as recently as 2010.
These are strong indicators of an underground terror network with links not just to local groups, such as the JI and Jemaah Ansharut Tauhid (JAT), but also the Islamic State in Iraq and Syria (ISIS), and possibly regional separatist groups in the Philippines, such as the Abu Sayyaf, as well as others in Southern Thailand.
That Malaysian police had on Friday arrested a suspected militant at a train station in the capital Kuala Lumpur, with weapons and documents linked to ISIS, is yet another sign of the long tentacles of the extremist group over South-east Asia.
ISIS has used the Internet, specifically social media sites and encrypted messaging platforms such as Telegram and WhatsApp, to promote its propaganda beyond the Middle East to North America, Europe, Africa, North Asia and South-east Asia.
With its high population of Muslims, South-east Asia has a strong appeal to ISIS, whose goal is to establish a global caliphate.
Threats of attacks after the siege in Paris last November that killed more than 130 people spooked capitals across the region to move into high alert as the world celebrated Christmas and New Year.
When Jakarta was hit by the five militants loyal to ISIS on Thursday - two weeks into 2016 - few could say they did not see it coming.
An Indonesian and Canadian were killed. Fortunately, no more lives were claimed, as the Indonesian police managed to take control of the situation in just 11 minutes.
While the brazen attack on the busy downtown street was shocking, the execution of the attack, however, seemed amateurish - even though at least one of the terrorists was said to have received weapons training.
CCTV footage of two of the attackers crouched next to a car outside a Starbucks cafe - ground zero of the siege - before being blown up by their own explosives, something initially thought to have been deliberate.
But a closer look at the video, which has since gone viral, seems to indicate that it may not have been their plan.
More may be revealed as the investigations unfold, but other details of the attack released by the police so far support the theory.
A forensic expert from the Indonesian National Police confirmed yesterday that the bombs used by the Jakarta five were of "low explosive" grade.
These included five unexploded bombs - containing explosives and items such as nails, bolts and ball bearings, which is a classic shrapnel configuration for home-made bombs - left behind by the attackers.
The five militants - four were killed by their own bombs while one was gunned down by police officers responding to the attacks - were said to be loyal to ISIS.
ISIS itself was quick to claim credit for the attack but the extent of their involvement, whether they had a hand in orchestrating it or worked through a proxy - which is the theory of the Indonesian investigators so far - is still unclear.
What is clear, however, is that more than anything, the Jakarta attack shows the imitative allure of ISIS attacks, both in style and impact, said counter-terrorism experts from New York-based security consulting firm The Soufan Group (TSG).
"Terrorist groups and individuals alike simply have to act in the name of the Islamic State to achieve a name for themselves," it said in a report released on Friday.
"Fortunately, the lethal impact of the Paris attack is not easy to replicate - as the Jakarta attack shows - as training, casing of targets, timing and execution are skills that need to be acquired."
However, training is now available for any aspiring militant in ISIS-controlled territories in Syria and that seems to be the place some 900 South-east Asian ISIS aspirants have left home for.
TSG believes the scourge of attackers hoping to emulate Paris will remain a pressing concern for cities across the globe as more attempts are likely in the future.
Indonesia's latest move to bar its own citizens believed to have travelled to ISIS territories from returning home may prove to be a game-changer.
For a country with more than 17,000 islands to police, however, that too may be a tall order.
This article was first published on Jan 17, 2016.
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