Western Mindanao Command spokesperson Major Filemon Tan Jr. said on Tuesday that the stronghold, located at Hill 355 in Barangay (village) Silangkum in Tipo-Tipo town, was fortified with bunkers, tunnels and foxholes.
The elite troops also seized two improvised explosive devices (IEDs), a battery, one small plastic box, switch and an improvised electric blasting cap.
On Sunday, combined troops from the Special Forces, Scout Ranger and Light Armor Cavalry troops, seized and controlled other strategic strongholds of the Abu Sayyaf in Barangay Baguindan and at Hill 440. It was fortified with seven foxholes, 12 bunkers capable of accommodating 80 persons.
Tan said the rebels were forced to abandon their stronghold after the assault with support from artillery fires.
The soldiers also recovered three unexploded ordnances and several IEDs.