Patrick Almodovar's head was found wrapped in plastic after his family did not provide ransom money. Maj. Filemon Tan, Armed Forces of the Philippines Western Mindanao Command spokesman, said Almodovar's head was discovered about 7:30 p.m. Wednesday.
Duterte, who has taken a hard line against suspected drug dealers, vowed to "destroy" the organization. Duterte has encouraged police officers and members of the public to pursue and kill, if needed, suspected drug dealers.
Duterte said his campaign against Abu Sayyaf will be different from that of previous administrations because it is "not just a campaign."
"I'll be harsh," he said. "Not just a campaign. Go out and destroy them."
"My orders to the police and to the armed forces against all enemies of the state, seek them out in their lairs, whatever, and destroy them," he said
Almodovar was abducted on July 16. Earlier this year, the group beheaded Canadians John Risdell and Robert Hall after ransom demands were not met.