Rep. Wahab Akbar died of wounds shortly after the blast late Tuesday, along with a lawmaker's driver and a legislative staffer. Seven other people, including two members of Congress, were wounded but were expected to recover.
Police said Akbar appeared to have been the target of the remotely detonated explosion, which shattered one of the entrances to the House of Representatives after a session had ended and lawmakers and their staff were preparing to leave.
Akbar, a former Muslim separatist rebel who became governor of southern Basilan province, joined the extremist Abu Sayyaf group in the 1990s when it had just embarked on a campaign to establish an Islamic caliphate in the southern Philippines, said metropolitan Manila police chief Geary Barias.
But as the group gained notoriety for attacks on Christians, ransom kidnappings and beheadings of hostages, Akbar disassociated himself from the group and joined U.S.-backed military operations against the militants on Basilan, Barias said.
In a speech at the House two months ago, Akbar had denied any links to the Abu Sayyaf, saying such allegations were "a lie told a thousand times" by the military, police and his political enemies.
He said the Abu Sayyaf violates Islamic teachings by stealing and attacking innocent civilians.
Top officials said the blast was not necessarily a revenge attack by the Abu Sayyaf.
Interior Secretary Ronaldo Puno said the investigation was "pointing away from a terrorist attack and more of a directed assault on a certain individual."
"There were threats on the life of Akbar," Puno told reporters. "The indications are that that was the case both in terms of location of the bomb and the manner it was set off."
Besides the Muslim rebels, Akbar also had many political foes, including those who ran and lost against one of his three wives who succeeded him as Basilan governor. Another wife won as mayor of the provincial capital of Isabela, while the other wife lost the race to become mayor of another town. He remained married to all three at the time of his death.
Political rivalries in the southern Philippines are often accompanied by bloodshed, and assassinations of politicians are common.
"Political angle, personal angle, it's too early to discount other possibilities," Barias said.
Akbar, 47, had said he joined his guerrilla father as a teenager in the Moro National Liberation Front, a Muslim rebel group that dropped its secessionist goal and signed a peace accord with the government in September 1996.
He later took up Islamic studies in Syria and underwent military training in Libya to become a preacher to the rebels and the people of Basilan. He also became a deputy guerilla commander with the MILF.
In 2002, as governor of Basilan, he welcomed U.S. troops who arrived on the island to train Filipino soldiers battling the Abu Sayyaf. Over the years, the island was gradually transformed from a militant hotbed into a showcase of counterterrorism success and humanitarian development.
The key Abu Sayyaf leaders were killed last year in a clash with Philippine marines on neighboring Jolo island. But some of the group's fighters regrouped and returned to Basilan, where they have joined with other guerrillas to stage sporadic attacks.
Barias said investigators suspected the bomb might have been hidden on one of two parked motorcycles and then remotely detonated as Akbar approached his car, mortally wounding him and ripping the motorcycles apart.
Investigators recovered parts of a cell phone, which may have been used to trigger the blast, he said.
President Gloria Macapagal Arroyo urged people not to jump to conclusions about the attack. "We're making a call against rumors, accusations that create confusion, fear and conflict," she said.
The blast occurred amid heightened political tensions in the country as Arroyo faces a third impeachment attempt in as many years.
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