Ronaldo Puno, the Philippine interior secretary, said an 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," he said.
"There were threats on the life of Akbar"
Ronaldo Puno, Philippine interior secretary
"The indications are that that was the case both in terms of location of the bomb and the manner it was set off."
Seven people were wounded when a remotely detonated bomb ripped through a section of the house of representatives on Tuesday.
Akbar, who represented southern Basilan island, later died of his injuries in hospital.
Attack 'an assassination'
He had two months ago denied having links with the Abu Sayyaf, saying the allegations were "a lie told a thousand times" by the military, police and his enemies.
Al Jazeera's Marga Ortigas, reporting from the scene in Manila, said investigators were calling the blast an assassination.
Geary Barias, Manila's police chief, said: "From what we saw, it looks like congressman Akbar was the target of the attack."
He said a parked motorcycle found in the rubble had had a bomb on it.
According to Joel Villanueva, a congressman, less than 50 of the 275 members of the house were inside when the bomb went off.
"It was a very huge explosion," he said. "We are stunned."
Akbar, 47, was a member of the Moro National Liberation Front, a Muslim separatist group that dropped its secessionist goal and signed a peace accord with the government in September 1996.
|Police said the bombing may not have been|
a revenge attack [AFP]
He was suspected of knowing the leaders of the Basilan-based Abu Sayyaf and later falling out with its commanders.
As governor of southern Basilan province, he had supported US-backed military operations on the island targeting the group.
The government calls the Abu Sayyaf "terrorists" and has blamed them for many bombings in the country.
Tuesday's explosion ripped through one entrance of congress just minutes after its evening session ended around 8pm (1200 GMT), sending debris flying across the parking lot.
Ortigas said many Filipinos, long suspicious of the administration of Gloria Arroyo, the president, felt the government was involved in many tactics to divert attention from allegations of corruption against the president and felt the bombinb may be another such tactic.
Arroyo, is facing her third impeachment complaint in as many years on Wednesday, said: "We're making a call against rumours, accusations that create confusion, fear and conflict".
The Philippine capital has been tense since a blast tore through a shopping mall in Manila's financial district last month, leaving 11 people dead and injuring over 100.
The owners of the mall have disputed police comments that the explosion was an industrial accident.