MANILA, Philippines – Two persons were confirmed dead while 23 others were injured when a bomb went off at the building of the Air Materiel Wing Savings and Loan Association (AMWSLAI) in Barangay Sta. Maria in Zamboanga City around 10 a.m. Thursday, officials said.

The explosion occurred while President Gloria Macapagal-Arroyo was to visit Tawi-Tawi province and US Ambassador Kristie Kenney was in Pagadian City, Zamboanga del Sur to inspect her government’s projects there.

Despite the incident, Malacañang said Arroyo was pushing through with her trip.

Shiela Covarrubias, city information officer, said the official count showed only two of the victims -- Eduardo Taliti of Cabatangan district in Zamboanga City and Ayesha Bosniot of Margosatubig, Zamboanga del Sur -- had died.

Colonel Darwin Guerra, commander Task Force Zamboanga, said one of the wounded has been confined to the Intensive Care Unit of a local hospital.

The cell phone-detonated bomb was apparently concealed in one of several bags of civilian commuters waiting to hitch a ride on an air force C-130 cargo plane outside Edwin Andrews Air Base in Zamboanga city, regional police director Chief Superintendent Jaime Caringal said.

Most of the wounded were civilian relatives of soldiers waiting in front of the AMWSLAI building to get a free ride on the Manila-bound C130.

Four engineers of the Alliance for Mindanao Off-grid Renewable Energy (AMORE) Program of the United States Agency for International Development (USAID) Area 1 project and two members of Zamboanga Representative Ma. Isabele Climaco’s staff were also wounded.

The AMWSLAI building, in Santa Maria village and just across Gate 1 of the Edwin Andrews Airbase, houses the offices of AMORE and Climaco.

Caringal said nobody had claimed responsibility for the powerful blast, which also damaged three parked cars.

"The blast was so powerful I fell to the floor from my seat in the office," Voltaire Mahatol, one of Climaco’s injured employees, told The Associated Press by telephone..

The explosion went off "a few meters" away from the gate of the airbase, Guerra said.

While the suspects behind the blast have yet to be identified, Guerra said: "This is definitely an act of terrorism."

Chief Superintendent Jaime Caringal said in a phone interview that the improvised explosive device (IED) was wrapped in a package placed near the AMWSLAI office.

Senior Superintendent Lorimer Detran, Zamboanga police officer-in-charge, said two children were among the injured.

Investigators were looking at the possibility that Al-Qaeda-linked Abu Sayyaf militants were involved in the attack. The militants have clashed in recent days with Philippine marines on nearby southern Basilan island.

"One possibility is that this is an Abu Sayyaf diversionary attack or a retaliation," Caringal said.

The Abu Sayyaf has targeted Zamboanga city, a predominantly Roman Catholic trading city, in the past. They were blamed by the police for two nearly simultaneous bombings that damaged a cathedral and a commercial building last April.

Caringal said he placed police forces in Zamboanga on alert and ordered more street patrols.

Security had already been tightened because several politicians were arriving in the city to register to run in August elections in an autonomous Muslim region in the south, he said.