The explosives were to be used in bomb attacks in Zamboanga City, 875 km south of Manila, according to a police report.

A joint team of police and military intelligence agents swooped down on the safe house of Abu Sayyaf's urban terrorist unit in the village of Rio Hondo in Zamboanga city Thursday, the report said.

The team seized about 100 pieces of "special detonators".

Soldiers and policemen also raided a second safe house in nearby Baliwasan Chico village, but the "bomb materials deposited (there) were already retrieved by an unidentified Abu Sayyaf member", the report added.

"Intelligence operatives are still conducting pursuit operations to recover the highly explosive materials," the police report said.

The raid was conducted after an Abu Sayyaf sub-commander who was arrested on April 11 revealed "that the group planned to conduct bombings in Zamboanga City with the equipment to be used in their activity already stored at the said safe-houses".

The Al Qaeda linked Abu Sayyaf has been blamed for some of the worst terror attacks and high-profile kidnappings-for-ransom in the Philippines, including the bombing of a passenger ferry in Manila in 2004 that killed more than 100 people.

--DPA