A bomb exploded at a pedestrian overpass near a school in the southern Philippines on Sunday, killing one person, wounding at least 16 others and raising concern that breakaway groups opposed to a peace deal are looking to destabilize the region.

Soldiers defused two other bombs near the scene of the first blast in the farming town of Kabacan in North Cotabato province, Police Senior Inspector Jarwin Castroberde said. Four of the victims were brought to a hospital in critical condition, according to Kabacan official David Saure. One later died, according to the local media.

Castroberde says investigators were trying to identify the attackers but the suspects include separatists opposed to a March peace deal between the Philippine government and the Moro Islamic Liberation Front (MILF), the largest insurgent group in the south of the largely Roman Catholic nation.

The deal stipulated that MILF would lay down their arms in exchange for more power in the south. In September, President Benigno Aquino III proposed a plan to give MILF the ability to run its own government in the marshy heartland of southern Mindanao region.

Although the deal to establish an autonomous zone with its own government and flag is still being worked out, Aquino is keen to see the deal in place before his term ends in June 2016.

Despite progress on the autonomous zone, scores of breakaway groups that have rejected the peace deal have continued occasional attacks against government forces and far-flung communities in the Mindanao region.

Abu Sayyaf is the most notorious breakaway separatist group, which split from MILF in the early 1990s. They are particularly active on Basilan Island. Although mainly known for kidnappings for ransom, they have also admitted responsibility for bombings, including an attack on a ferry in February 2004 that killed more than 100 passengers.

The four-decade conflict in the southern Philippines is one of the world’s bloodiest, with a death toll estimated to have surpassed 150,000.

Al Jazeera and wire services