Speaking to popular local news website Rappler, the president said that he has been informed about cousins of his who may have pledged allegiance to or joined Daesh (ISIL/ISIS) in Mindanao, the Philippines southernmost major island.
Recalling that he himself was from the island of Mindanao, and is a descendent of the Moro– a term for the Philippines' Muslim population, Duterte noted that he has received news of family members belonging to the terrorist group.
"Let's be frank: I have cousins on the other side," the president said. "They are with the MI [Moro Islamic Liberation Front] and the Moro National Liberation Front. Some, I've heard, are with ISIS," he added.
"You are you and I am me, and I said, 'if we meet in one corner, so be it,'" he added, alluding to harsh repercussions for anyone who would violate the country's laws, whether they are relatives or not.
Duterte complained that "ISIS seems to be everywhere," referring to a string of terror attacks which have plagued the country, including a blast outside a church on Christmas Eve. "In Samal, there was an explosion. In Midsayap, while the priest was giving a sermon on extrajudicial killings, his church was bombed," the president said.
In November, in a live televised address, Duterte confirmed that the Maute Group, an Islamic fundamentalist terror group, had links with Daesh. Maute Group members are thought to have been responsible for the bombing of a night market in Davao City in September.
After the market attack, the Philippines' president, well-known for his striking use of language, promised to literally "eat" the perpetrators alive. "I'm not kidding," he stressed, adding that "these guys are beyond redemption."
Last week, Duterte presided over a meeting with military and police officials to discuss the string of bombings plaguing his country. He also confirmed to Rappler that he had discussed the threat posed by Daesh with other world leaders. "Yes, [it was] part of our discussions," he said.
Security forces in the Philippines have engaged in a campaign against Islamist-inspired terrorist groups in the south of the country. Daesh has pledged to turn Mindanao Island into a province in their Southeast Asian 'caliphate'.
In August, Duterte also made headlines after pledging to be "ten times" as brutal as Daesh, explaining that it was difficult to combat the threat when dealing with a group that doesn't know or "have [the] concept of risk." The president warned the group that he would "never allow [his] country to be destroyed" by terrorists.
Duterte is known worldwide for his harsh zero-tolerance policy in dealing with the country's drug problem, allowing security forces to engage in the extrajudicial killing of drug dealers and other criminals. That policy, combined with the president's harsh language in relation to foreign leaders, has led to Duterte being criticized and condemned by many Western officials and media resources.