A former Muslim rebel turned congressman who backed a U.S.-Philippine offensive against Muslim militants was killed late Tuesday along with a lawmaker's driver and a congressional staffer when a bomb exploded at an entrance of the Philippine House of Representatives, police said.

The remotely detonated bomb toppled the ceiling at the entrance, damaged cars and injured seven other people, including two congresswomen. Their injuries were not life threatening.

Interior Secretary Ronaldo Puno said the target appeared to be Rep. Wahab Akbar, former governor of southern Basilan province who threw his support behind U.S.-backed military operations targeting al-Qaida-linked Abu Sayyaf rebels. Akbar died of wounds in a hospital, police said.

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Puno, however, sought to downplay the possible involvement of Muslim extremists, saying the investigation is "pointing away from 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."

Akbar, 47, was a member of 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.

Some security officials have suspected that Akbar knew the leaders of the Abu Sayyaf, a Muslim radical group that has its roots on Basilan island. But they said he later had a falling out with Abu Sayyaf commanders and started fighting them.

Akbar was Basilan governor when U.S. troops arrived there in 1992 to train and equip Filipino soldiers battling Abu Sayyaf militants. Over the years, the island province was gradually transformed from a terrorist hotbed into a showcase of counterterrorism cooperation 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 militants have regrouped and returned to Basilan, where they joined hands with other guerrillas to launch sporadic attacks.

Akbar, who is remembered among Basilan civilians for strong-arm tactics against the militants, also had an array of political opponents, including ones who ran against one of his wives who succeeded him as governor of Basilan. Political rivalries in the southern Philippines are often solved with readily available weapons, and assassinations of politicians are common as part of long-running vendettas and feuds locally known as "rido."

At the House of Representatives, Razon said a destroyed motorcycle was found and experts were conducting chemical tests to find out if it was used to carry the bomb.

"I felt the blast although I was on the other side of the building. The ceiling of the canopy near the south wing entrance came down," Rep. Teodoro Casino told The Associated Press.

Puno said authorities were treating the blast as "as a violent crime intended on a particular individual rather than any institution."

President Gloria Macapagal Arroyo said while police investigate and bolster security, "we're making a call against rumors, accusations that create confusion, fear and conflict."

"If this is terrorist action or work of an anarchist I'm sure it was deliberately done to cow us," House Speaker Jose de Venecia told reporters at the site.

The blast occurred amid heightened political tensions in the country. Arroyo is facing a third impeachment complaint in as many years.

"We cannot rule out anything until the investigation is completed," de Venecia said. "There are many threats to us personally and officially. We will have to decide whether we have to augment security."

"We are not afraid (and) we want the situation to normalize as quickly as possible," he added.

The Philippine capital has been jittery since last month, when an explosion damaged a shopping mall in the financial district, killing 11 people and injuring more than 100. A preliminary police report said it was an accident, although the owners of the mall disputed the finding.