By Roy Ramos & Hader Glang

ZAMBOANGA CITY

Philippine security forces were on full alert in key southern cities Wednesday, after four separate explosions wounded 16 people the day before in Mindanao – the country’s second largest and southernmost major island.

Supt. Rolly Octavio, deputy city police director, said Wednesday that security measures had been doubled after eight people were injured by a bomb attack outside the City Hall of General Santos, a regional commercial hub known as the center of the country's tuna industry and the hometown of boxing icon Manny Pacquiao.

“We’re still determining what type of grenade was used and its materials. We don’t want to speculate as to the motive and the identity of the suspects so we’re considering all possible angles,” Octavio said on a local television program.

Maj. Gen. Eduardo Ano, chief of the army’s 10th division, said the Bangsamoro Islamic Freedom Fighters (BIFF) may be responsible since the explosive’s signature was similar to those previously used by the rebel group.

Mayor Ronnel Rivera interrupted his trip to Davao City, rushing back to General Santos City after the explosion.

Ordering law enforcement units to speed up the investigation, Rivera said, "I want to pin down immediately whoever are behind this blast.”

“This blast will somehow be a deterrent to the vibrant economy of the city, especially to the entry of investments,” he added, calling on residents to be strong and to not point fingers.

Another attack destroyed a warehouse Tuesday in Lamitan City in Basilan province – a known stronghold of the al-Qaeda-linked Abu Sayyaf – after four people riding a motorcycle threw a fragmentation grenade, according to Superintendent Noel delos Reyes, police chief of the greater Autonomous Region in Muslim Mindanao.

Lamitan police chief Sr. Insp. Gean Gallardo said they suspect Abu Sayyaf extortionists to be behind the attack, in which no one was wounded.

In Cotabato City, five people – including a soldier – were injured when an explosive went off inside a vehicle parked near a plaza.

The vehicle’s owner, Mindanao State University Professor Ismael Abdullah, was at a pharmacy at the time of the explosion, and told police investigators he knew nothing about the motive behind the explosion.

Maj. Dante Gania, public affairs officer of the army’s 6th Infantry Division, said the attack was probably carried out by Abu Sayyaf bomb expert Basit Usman since the bomb’s manufacture matched his style.

An in-depth investigation to determine the motive and the explosive used is ongoing, according to police director Senior Superintendent Rolen Balquin.

A month ago, an intelligence official had warned of reported plans by Usman's group to detonate car bombs in regional cities – such as Cotabato, Cagayan de Oro, Iligan, and Davao - in retaliation for a raid by government troops in Mamasapano town.

Meanwhile, a roadside bombing blamed on communist rebels in Magpet town in Cotabato province injured three policemen Tuesday morning.

Captain Manuel Gatus, civil-military relations chief of the army’s 57th Infantry Battalion, confirmed that the officers had been headed to Natutungan village to verify reported sightings of New People’s Army (NPA) guerrillas when an explosive was detonated as their vehicle passed.

The NPA, which has been waging an insurgency since 1969 that has left tens of thousands of people dead, has conducted more than a dozen roadside bombings in nearby towns in the past ten months.

The explosions Tuesday come as authorities are keeping close watch on reports that Islamic State of Iraq and Levant (ISIL) militants have recruited members of the BIFF in the Muslim south.

BIFF - through its spokesman Abu Misry Mama - confirmed Monday that it had pledged allegiance to ISIL and was in constant communication with the group.

BIFF opposes talks between the government and the Moro Islamic Liberation Front (MILF), who signed a March 27 peace deal that brought to a close 17 years of negotiations and ended a decades-old armed conflict in Mindanao while granting Muslim areas greater political autonomy.

Since breaking away from the MILF in 2008, the BIFF has vowed to destroy the peace process with its head Ameril Umbra Kato leading attacks in Mindanao.

The Abu Sayyaf has also recently pledged support to ISIL in videos posted on Youtube.

A video posted in late July that opens with al-Qaeda’s symbolic black flag shows senior Abu Sayyaf leader Isnilon Hapilon – who carries a $5 million U.S. bounty on his head and has been indicted in Washington for “terrorist acts” against foreign nationals - alongside masked men pledging allegiance to ISIL.

The links, however, have yet to be verified by the Philippines' military.

Since 1991, the Abu Sayyaf -- armed with mostly improvised explosive devices, mortars and automatic rifles -- has carried out bombings, kidnappings, assassinations and extortions in a self-determined fight for an independent Islamic province in the Philippines.

It is notorious for beheading victims after ransoms have failed to be paid for their release.

www.aa.com.tr/en