Editor's note: Maria Ressa is CNN's former Jakarta bureau chief and author of "Seeds of Terror: An Eyewitness Account of Al-Qaeda's Newest Center of Operations in Southeast Asia." She worked as a journalist in Southeast Asia for nearly 25 years, most recently for ABS-CBN. In February, she becomes the first Author-in-Residence at the International Center for Political Violence & Terrorism Research (ICPVTR) in Singapore.
(CNN) -- Last week's bus bombing in the Philippines highlights how bomb-making techniques brought into the country by al Qaeda and its associate groups can be harnessed by multiple interests.
This year marks the tenth anniversary of the 9/11 attacks, a symbol of al Qaeda's global strength and coordination. It triggered the unmasking of Jemaah Islamiyah or JI, which effectively functioned as Al-Qaeda's arm in Southeast Asia, co-opting homegrown groups for its attacks.
What happened to Jemaah Islamiyah paralleled what happened to al Qaeda after 9/11: Their centralized command structures collapsed, and their operational capabilities were degraded by the arrests of top and mid-level leaders.
Still, the old networks remain and continue to spread their radical ideology. The cells carry out attacks without central leadership. The training camps are smaller and operate in a more ad hoc manner. It became like the communists' guerrilla warfare -- Robert Taber's war of the flea. The threat is more dispersed and harder to track down. The lines between groups are more fluid as they factionalize and splinter.
In the Philippines, Jemaah Islamiyah brought in new bomb-making technology starting in the late '90s, training members of three Muslim groups: the Moro Islamic Liberation Front (MILF), the country's largest Muslim separatist group; the more radical Abu Sayyaf Group (ASG), which received training in the mid-'90s from al Qaeda; and the Rajah Solaiman Movement or RSM, Christian converts to Islam.
Over time, some hard-core MILF fighters turned to crime. Asian and western intelligence officials say members of the MILF's Special Operations Group (MILF-SOG) splintered and formed Al-Khobar, an extortion team operating in the southern Philippines which targets bus companies. In 2008, an arrested member of Al-Khobar admitted their group is led by an MILF field commander.
The MILF has repeatedly denied any institutional links to Al-Khobar or any other terrorist groups. It says the MILF-SOG does not exist. However, documentary and testimonial evidence shows as early as 2000, the MILF-SOG was working with Jemaah Islamiyah on a series of bombings in Manila (Rizal Day bombings).
The Abu Sayyaf Group or ASG carried out the Philippines' worst terrorist attacks from 2002 to 2005, including the Superferry bombing in 2004 (one of the world's worst maritime terrorist attack) and coordinated, near simultaneous Valentine's Day bombings in Manila, Davao and General Santos City in 2005.
In the succeeding years, however, most of ASG's activity also turned to crime -- turning kidnapping for ransom into a cottage industry. Security and intelligence sources estimate at least US $1.3 million was paid in ransom in 2010 alone.
The Rajah Solaiman Movement or RSM are Christian converts to Islam. Their base of operations was on the island of Luzon, particularly the capital, Manila. Around 2003, however, intelligence officials say they effectively merged with the ASG, expanding its reach to the capital allowing ASG to carry out the Superferry and the Valentine's Day bombing.
This is the context for the January 25 bus bombing in the capital's financial district, Makati, which killed five people and injured at least 14.
It happened about a block away on the same street as the 2005 Valentine's Day bombing in the capital - also an explosion on a bus. Philippine National Security Adviser Cesar Garcia told the ABS-CBN News Channel (ANC) that Tuesday's bombing had many similarities to the attack six years earlier.
"An investigation of the 2005 Valentine's Day bombing showed the suspects rode the bus, carried the (bomb) in a backpack, left the backpack, got off (and) detonated the bomb with the use of a cell phone," Garcia told ANC.
In 2005, the ASG quickly claimed responsibility for the attacks. Authorities arrested several suspects, and eight months later, an Indonesian JI member (who claimed he was a member of both JI and ASG) and two Filipino members of ASG (who were also members of RSM) were convicted for the 2005 bus bombing. Coincidentally on Tuesday, the Philippine Supreme Court upheld their convictions of life imprisonment.
Although last week's bombing may seem similar, authorities caution against jumping to conclusions.
There are at least two reasons why:
First, bus bombings are a trademark of Al-Khobar, which operates on the southern island of Mindanao, and was blamed for the last major bus attack, which happened last October. Authorities said it used an 81-mm mortar round remotely detonated by a cell phone. Tuesday's attack used an 81-mm mortar round triggered by a cell phone.
Since Al-Khobar is formed by members of the MILF-SOG, is the MILF involved? A top government official seems to hint that may be the case. Although the MILF denied any involvement in last week's blast, Justice Secretary Leila de Lima said Thursday that the bomb - according to police and military intelligence reports - "bears the signature of the Moro Islamic Liberation Front Special Operations Group" (MILF-SOG). MILF spokesman Eid Kabalu told ABS-CBN these intelligence reports "are misleading."
An interesting note: Last year, officials blamed Al-Khobar for the October bus bombing but avoided mentioning the MILF because of ongoing overtures for peace. For the first time today, Justice Secretary de Lima said that attack was the work of the MILF-SOG. Officials involved in the investigations say a possible motive could be to derail the peace talks slated to begin in February.
The second reason for caution is related to politics. Last week's bombing happened in an overheated political environment -- when members of the security forces are themselves under investigation. One ongoing senate investigation is questioning corruption in the military, while the police is under pressure after a series of grisly murders and "carjacking" incidents.
Intelligence sources say the elements identified in Tuesday's blast -- the mortar round, the cell phone detonator -- are well known and could easily be replicated by groups that may intend to destabilize the government of President Benigno Aquino III or divert attention away from these ongoing investigations.
Secretary de Lima acknowledged this possibility saying the government is investigating members of the police and military as well.
Last week's bombing comes three months after six nations -- the United States, Australia, Great Britain, Canada, France and New Zealand -- warned about possible attacks in the Philippines and its capital, Manila.
What's clear is that the terrorism threat has evolved in the Philippines, and the situation has grown far more complex.
The opinions expressed in this commentary are solely those of Maria Ressa.