ZAMBOANGA CITY, (AA): Philippine authorities have blamed a powerful bomb explosion that killed a girl and injured more than 30 other people in the country’s Muslim south on an al-Qaeda-linked militant group.

The mayor of predominantly Christian Zamboanga City said Saturday that the Abu Sayyaf group’s (ASG) involvement in Friday’s blast surfaced after a police investigation showed the group had demanded an initial payment of P500,000 ($10,750) and P20,000 monthly from the Biel Transport Company for “protection”.

“Police form ‘Task Force Biel,’ eye ASG [Abu Sayyaf] Basilan [province] as responsible for bus explosion with extortion as motive,” Isabelle Climaco-Salazar said in a statement. “Biel bus explosion linked to Lamitan [town] blast last Sept. 16.”

The explosion ripped through a bus Friday afternoon at a crowded market bus terminal while passengers were alighting from the vehicle.

Police reported that an 11-year-old girl was killed in the attack that injured 33 other people, most of them children.

Climaco announced Saturday that the city government is offering a P200,000 reward for information leading to the arrest of those responsible, and called on all bus companies and other public transportation to enforce strict inspection, safety and security procedures.

In the statement, issued from China where she is attending the 12th China-ASEAN Exposition, Climaco condemned the attack as an act of injustice against Zamboanga — especially the victims.

Citing an intelligence report, the city’s police director, Sr. Supt. Angelito Casimiro, told a meeting at City Hall late Friday that an attack had been expected following the Sept. 16 explosion near a gas station in Lamitan city in the nearby island province of Basilan – a known Abu Sayyaf stronghold.

“I hate to say this, but we were expecting this,” he said, adding that civilian sources had provided vital information in linking the two attacks, both believed to be part of the Abu Sayyaf’s extortion activities.

He said Chief Supt. Miguel Antonio Jr., regional police director, had ordered the creation of a special investigation task group to lead and supervise the “thorough inquiry, scrutiny and analysis of the latest bomb explosion.”

Casimiro held the Basilan-based Abu Sayyaf group responsible due to its notoriety for extortion activities, while its counterpart in the nearby island province of Sulu is known for kidnapping activities.

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.

[Photo: A soldier is seen near the site of a powerful bomb explosion at a crowded market bus terminal in the Philippines’ Muslim south, Zamboanga, on September 18, 2015. Photgrapher: Remus Ong/AA]