The eccentric leader pulled no punches when addressing the jihadi fighters currently attempting to gain a foothold in the south of the country.
He said he would eat their organs in front of them with “salt and vinegar” in an outrageous tirade this week.
Mr Duterte said: "I will eat your liver if you want. I will just add salt and vinegar, I will eat it in front of you.
“You want to be enslaved by these? Son of a b***h. Let’s just circumcise ourselves again.
“What are you really trying to prove with these actions? You take the name of Allah in vain?
“You use the name of God to kill people that way.”
It comes after two Vietnamese sailors were found beheaded in Marawi by the killer ISIS jihadis in the south of the country.
They are believed to be part of a group of six sailors kidnapped last November and held captive by an ISIS cell.
Philippines military forces are trying to retrieve the final three sailors, after one escaped during a previous rescue mission earlier this year.
Mr Duterte has repeatedly grabbed the headlines with his bizarre and often vulgar outbursts.
In fact this isn’t even the first time he has vowed to eat the livers of his extremist enemies, promising a similar stunt in April.
He warned he could be “50 times” more brutal than Islamic extremists as he promised to eat their vital organs if they are captured by his troops.
Mr Duterte warned: “If you want me to be an animal, I’m also used to that. We’re just the same. I can dish out, go down what you can 50 times over.
“Just drive me to extreme anger, and I can eat a person. Give me salt and vinegar and I’ll eat his liver.
“You know, I am capable of eating a person. If you anger me, in truth, I will eat you alive. Raw.”