Speaking to the local Filipino community in the Vietnamese city of Danang yesterday, Duterte also threatened to slap a UN rights rapporteur if he met her, and used obscene language to hit back at critics of his deadly drugs crackdown.
"When I was a teenager, I would go in and out of jail. I'd have rumbles here, rumbles there," said Duterte, who is in Danang for the Asia-Pacific Economic Cooperation (APEC) summit.
Duterte won last year's presidential elections after promising to eradicate illegal drugs with an unprecedented crackdown that would see up to 100,000 people killed.
Since he took office 16 months ago, police say they have killed 3,967 people in the crackdown. Another 2,290 people were murdered in drug-related crimes, while thousands of other deaths remain unsolved, according to government data.
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Duterte, 72, remains popular with many Filipinos who believe he is making society safer.
The firebrand leader consistently generates headlines for his abusive language and incendiary comments defending the drug war.
Duterte said last year he would be "happy to slaughter" three million drug addicts.
Duterte also said in December last year that he had personally shot dead criminal suspects when he was mayor of southern Davao city to set an example to police.
His spokesman later sought to clarify the remarks, saying those killings were during a "legitimate police action".
Duterte's aides have repeatedly told journalists not to believe everything the president says, cautioning that he often jokes or indulges in "hyperbole".
His latest comments come ahead of him hosting US President Donald Trump and other leaders for the Association of Southeast Asian Nations (ASEAN) summit.
Trump is due to fly into Manila from Vietnam along with many other leaders on Sunday evening, ahead of two days of talks.