MANILA (Reuters) - The Philippine army has detained a Spanish man it said had been caught with explosives on an island notorious as a stronghold of a militant group closely linked to Islamic State.

Abdelhakim Labidi Adib, 20, was stopped on Monday at a checkpoint on Basilan, home to an extremist faction of the Abu Sayyaf group that was led by Isnilon Hapilon, Islamic State’s “Emir” in Southeast Asia, until his death in October.

Adib is suspected of being an extremist sympathizer and was detained without charge, as permitted by martial law, which is in force across the Mindanao region, where Basilan is located.

Captain Exequil Panti, head of the special forces on Basilan, said Adib was not initially a suspect but had been stopped because he was with another man believed to be an Abu Sayyaf member.

Panti said the men ran away from troops and Adib threw aside his backpack, which was later found to contain detonators, blasting caps and grenades. The other man escaped, Panti said.

Adib said he was a tourist and denied owning the bag during questioning at the justice ministry in Manila on Wednesday, where media were also present.

“I am innocent of the accusation against me,” he said. “The accusation is not true.”

Basilan is a no-go area for most Filipinos and Western countries typically warn citizens to stay away, because of the penetration of Abu Sayyaf and fierce military offensives against its fighters.

Abu Sayyaf is also notorious for making vast sums of money from piracy and kidnapping. Canadians and a German were among the Westerners beheaded by Abu Sayyaf when ransoms were not paid.