But Philippine authorities have said that the Abu Sayyaf is mainly a criminal gang engaged in kidnappings for ransom and other lucrative illegal activities.

The group has kidnapped dozens of foreign aid workers, missionaries and tourists in the south. By demanding and getting millions of dollars in ransom money, the group was able to raise funds to buy more arms. Just like the IS, the Abu Sayyaf is known for its brutal reputation of beheading some of its captives, including an American tourist seized in 2002.

Among the hostages still being held captive by the Abu Sayyaf are two European birdwatchers, a Malaysian fish breeder, and an elderly Japanese man.

Last year, the group released retired Australian soldier Warren Rodwell and Jordanian journalist Baker Atyani after ransoms were reportedly paid. The two were abducted separately and each held captive for over a year.

Local analysts here have long expressed wonder why despite its superior strength and resources, the Philippine military cannot defeat the Abu Sayyaf which has only a few hundred armed combatants.