Philippines Army Lieutenant Colonel Jonas Templo said an improvised explosive was detonated in the early hours of the morning, in the Sitio Maganda neighborhood of Lamitan, a city in Basilan province.
Basilan Governor Jim Salliman said at least five others were wounded by the attack, which used a van and targeted a checkpoint manned by a Citizen Armed Force Geographical Unit (CAFGU) -- a paramilitary contingent which included military and civilians.
Salliman said the Armed Forces of the Philippines told him Abu Sayyaf was responsible for the blast.
Mindanao -- the Philippines' southernmost major island, on which Basilan sits -- is home to several Islamist insurgent groups, including Abu Sayyaf, which has been blamed for a number of attacks on civilians and Philippine government troops, as well as the kidnapping of several foreign nationals.
Abu Sayyaf -- alongside the Maute group, another Mindanao-based terror organization -- was responsible for the invasion and occupation of Marawi, the country's biggest Muslim-majority city, in 2016.
Abu Sayyaf Basilan was led by militant Isnilon Hapilon until his death in the siege of Marawi. The group pledged allegiance to ISIS in 2014.
Greater autonomy promised
The attack comes soon after Philippines President Rodrigo Duterte approved the Bangsamoro Organic Law (BOL), creating an autonomous region in majority-Muslim areas of Mindanao.
The law, which gives greater independence and autonomy to Muslims in the predominantly Catholic Philippines, is the culmination of decades-long peace negotiations between Mindanao-based rebel groups, including the Moro National Liberation Front (MNLF) and the Moro Islamic Liberation Front (MILF) and the national government, according to CNN Philippines.
Duterte has said that he will not negotiate with Abu Sayyaf or other Islamist militant groups.
The new law will abolish the current Autonomous Region in Muslim Mindanao (ARMM), which was called a "failed experiment" by former Philippines President Benigno Aquino, to make way for the new autonomous Bangsamoro government.
Under the BOL, the region will elect its own 80-member parliament and have significant fiscal autonomy from the central government.
Duterte, the first Filipino premier to hail from Mindanao, signed the bill into law earlier this month. It will take effect in early August.
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