North Cotabato Gov. Emmanuel Piñol said Usman Kasim, alias Commander Osas, was arrested by combined elements of the Armys 602nd Infantry Brigade, 2nd Marine Brigade and the local police.
According to military intelligence sources, Kasim, a member of the Moro Islamic Liberation Front (MILF), underwent extensive training in the handling of explosives at a camp at the Pakistan-Afghanistan border five years ago.
Kasim is the fourth suspect arrested in connection with the bus terminal bombing.
One of them, Abu Hashim Solaiman, said to be another bomb expert of the MILF, has gone missing after being allowed to post bail two months after his arrest.
Kasim, however, has denied any involvement in the bombing, claiming he is just an ordinary worker of a bus company plying the Cotabato-Davao route.