ZAMBOANGA, Philippines -- Muslim militants linked to al-Qaida may be responsible for bombings Thursday that killed six people, injured 144 and devastated two department stores in this Christian city, the military said.

Suspicion fell on Abu Sayyaf because of similarities to an Oct. 2 blast that killed four, including an American Green Beret. That explosion was blamed on the Muslim extremists notorious for kidnappings and murders. TNT was apparently used in both attacks.

Thursday's bombings, 30 minutes apart, came less than a week after three bombs exploded on the Indonesian island of Bali, killing 183 people.

There was no claim of responsibility for the attacks in Zamboanga, but military spokesman Lt. Col. Danilo Servando said suspicion fell on an Abu Sayyaf faction headed by Khaddafy Janjalani, one of five leaders of the group indicted by Washington for a mass kidnapping last year that left 18 hostages dead, including two Americans.

Government officials have said Abu Sayyaf may have links with Jemaah Islamiyah, another Islamic militant group in Southeast Asia that allegedly has ties with the al-Qaida terror network.

On Thursday, Indonesian police named Abu Bakar Bashir, the spiritual leader of Jemaah Islamiyah, a suspect in a series of church bombings across Indonesia on Christmas Eve 2000. The group has been linked by reports to the Bali bombings last weekend.

Days before the Oct. 2 bombing, Abu Sayyef had threatened attacks in retaliation for a military offensive against it.

In linking Abu Sayyaf to al-Qaida, Philippine officials have cited alleged attempts by Osama bin Laden's lieutenants to provide the guerrillas with training on explosives and weapons handling in past years.

Thursday's attack turned the usual early afternoon bustle of Zamboanga's downtown area into a gory scene of debris, blood and chaos. Panicked shoppers scattered as police cars and pickup trucks were mustered into ambulances to ferry wounded people to hospitals that were quickly overwhelmed.

Packages examined

Nervous police bomb squads blew up five suspicious packages, but further examination found they contained no explosives.

President Gloria Macapagal Arroyo condemned the latest terrorist strike to hit her impoverished country, a key supporter in the U.S. war on terrorism.

Some 260 American troops are in Zamboanga, a predominantly Christian city of 600,000 in the violence-wracked southern Philippines, after a six-month counterterrorism training exercise to help local troops fight the Abu Sayyaf.

No foreigners were believed to have been injured in Thursday's bombings.