MANILA, Philippines (AP) — The Philippine military says a soldier and four militiamen have been killed by a powerful bomb that exploded while the troops were inspecting a suspicious van on a southern island.

Regional military spokesman Lt. Col. Gerry Besana says two other government militiamen were wounded in the blast after dawn on Tuesday near an army militia outpost in the village of Colonia on the island province of Basilan.

Police say the blast occurred after militiamen flagged down the van at a checkpoint for inspection, although the report had limited details and it's unclear what happened to the driver.

No group has claimed responsibility.

Regional military commander Lt. Gen. Arnel Dela Vega committed "every available resource under his disposal to identify the perpetrators in the soonest possible time."