Philippine President Gloria Arroyo says investigators are tracking down suspects in Thursday's deadly bomb attacks in the southern city of Zamboanga. Another Philippine official says the investigation is focusing on the Abu Sayyaf and the al-Qaida terror network.

President Gloria Macapagal Arroyo spent Friday surveying the site of the Zamboanga attacks and visiting the injured. After a briefing with the military, Ms. Arroyo announced that investigators had identified four suspects and are hunting them.

Seven people died in the attacks. Around 150 people were injured when two bombs exploded in adjacent shopping centers.

Zamboanga's congressman, Celso Lobregat, said no one has claimed responsibility for the attacks but investigators are focused on two terror groups. "They have not yet identified which group. Nobody has claimed responsibility," he said. "They are looking at two angles, one is the Abu Sayyaf and one is al-Qaida group."

Zamboanga, a mostly Christian city in a predominantly Muslim area, has suffered several bomb attacks in the past few years. A bomb three weeks ago in Zamboanga killed three Philippine citizens and a U.S. soldier.

Several of the attacks have been blamed on the Abu Sayyaf guerrillas, a militant Islamic group notorious for kidnappings and murders. The United States says the group has links to the al-Qaida network, which is considered responsible for last year's September 11th attacks.

Philippine National Security Adviser Roilo Golez says as many as 20 people have been questioned in connection with Thursday's bombing, but none have been arrested.

Investigators also are combing through the blast area, looking for clues. "They're collecting bits and pieces of the debris and everything," said Mr. Golez. "They're now undergoing laboratory examinations." He dismissed connections between the Zamboanga attacks and a grenade that exploded Friday in Manila's financial district. No one was injured in that blast.

The Zamboanga blasts came just days after bombs killed at least 180 people on the Indonesian island of Bali. No one has been arrested in that attack, and thus far, it does not appear the Philippine and Bali bombings are linked.