President Duterte said a woman who remains at large left a device that exploded during mass at the cathedral in the remote Muslim-majority island of Jolo on Sunday, and her husband later blew himself up outside
Investigators probing the Catholic cathedral bombing that killed 21 people in the Philippines' restive south said Monday a group tied to notorious Islamists Abu Sayyaf is the prime suspect.
Two explosions tore through the cathedral on the Muslim-majority island of Jolo, killing worshippers at Sunday mass and security forces in an attack claimed by the Islamic State group.
Authorities said the so-called Ajang-Ajang faction is a small band of several dozen that most likely carried out the bombing, the Philippines' worst in years, in an act of revenge.
"Last year their leader was killed. There have been persistent reports that they will retaliate," regional military spokesman Lieutenant Colonel Gerry Besana told AFP.
"Yes, we saw them in the CCTV. It was the brother of the leader who was killed," he said referring to footage from outside the cathedral. "He was seen with two other members of Ajang-Ajang."
Security forces say the group is composed of relatives of Abu Sayyaf kidnap-for-ransom group members who have been killed in clashes with the government.
Abu Sayyaf, which is based on the remote Jolo island, has been blamed for the Philippines' deadliest attack, a 2004 ferry bombing in Manila Bay that claimed 116 lives.
- 'Revenge group' -
"There are high-level law enforcement operations against them (Ajang-Ajang)," said Rommel Banlaoi, chair of the Philippine Institute for Peace, Violence and Terrorism Research. "It evolved into a revenge group."
While Abu Sayyaf have sworn allegiance to Islamic State, that is not necessarily true for the motley members of Ajang-Ajang.
"Not all members of Ajang-Ajang group are pro-ISIS, but all of them are Abu Sayyaf group," said Banlaoi using another acronym for IS. "It's not IS-affiliated."
The IS claim, in a formal communique, said two suicide bombers had detonated explosive belts, according to the SITE Intelligence Group, which monitors jihadist activities.
But a military report said a second bomb that went off at the cathedral was left in the utility box of a motorcycle in the parking area outside.
Police said they believe the explosives were likely detonated remotely, but did not elaborate. Despite the contradictions, authorities have not ruled out IS involvement.
Regardless of who staged the bombing, concern was growing Monday over the impact it will have on a decades-long push for peace that culminated last week in voters approving expanded Muslim self-rule in the south.
The vote was the result of negotiations started in the 1990s with the nation's largest rebel group, the Moro Islamic Liberation Front (MILF), and will give it considerable power over the so-called Bangsamoro region.
"This is a big challenge for the Bangsamoro government," said Banlaoi.
The former rebels need to show they will be able to pull the region toward peace in order to attract much-needed investment to alleviate poverty and counter extremism, he told AFP.
"MILF needs to prove it can make a difference... the gravity of the problem faced by MILF is wow, so overwhelming," he added.
- 'Squandered opportunities' -
The church attack came despite President Rodrigo Duterte, who visited the cathedral Monday, putting the southern Philippines under martial rule after pro-IS militants seized the southern city of Marawi in May 2017.
Government officials have argued that martial rule, which gives authorities extra powers, has been effective in taming the perpetually restive region.
But families of the dead, who began holding funerals on Monday, have become the latest in the Philippines' south to mourn loved ones killed in a bomb attack.
"My 81-year-old mother does not deserve this kind of death," Edward Non told AFP, with a row of victims' coffins behind him.
"This has to stop. It's the innocent civilians who suffer."
Experts were also worried about how the bombing would impact the hopes for new development in the region, which were spurred by the self-rule vote victory.
"It's a terrible human tragedy, it's also a development tragedy," World Bank economist Andrew Mason told broadcaster ABS-CBN.
"When we see conflict areas, when we see ups-and-downs and negative impacts due to violence and conflict, what we see is also these are development opportunities that are squandered."