Just over a thousand guerrillas are turning in 940 weapons in a single day, in a graduated decommissioning process that aims to turn the Moro Islamic Liberation Front (MILF), the country's largest rebel force, into a regular political party.

The fighters demobilised on Saturday represent a symbolic first step toward retiring what MILF says is a force of 40,000 fighters in the coming years.

"The war is over... I have no firearms left," Paisal Abdullah Bagundang, 56, a self-described veteran of more than 100 firefights with government security forces since the 1970s, told AFP.

But the disarmament will take time to make an impact in a place where violence is an almost daily threat.

A bomb hidden in a parked motorcycle exploded near a public market in Isulan town early on Saturday, just hours before President Rodrigo Duterte was to witness the decommissioning ceremony some 40 kilometres (25 miles) away in Sultan Kudarat.

Police said eight people were injured in the attack by unknown suspects.

The decommissioning process "should not lead to expectations that it is going to result in a major deceleration in attacks", said Francisco Lara, senior conflict adviser for Asia at watchdog group International Alert, noting that the general public in the region are also armed.

Officials hope putting rebel weapons "beyond use" will nudge the region away from the mindset that gun-ownership is essential to ensuring survival.

About a third of MILF combatants and their weapons are to be retired in the first phase of the decommissioning process.

"In order to have an enduring peace, we have to change the mindset of the people," Duterte peace adviser Carlito Galvez told reporters Friday.

Each retired fighter will receive a million pesos' (about $19,000) worth of cash, scholarships, health insurance, and training to become productive civilians.