Duterte, a firebrand ex-mayor and former prosecutor who led the Philippines from 2016 to 2022, was arrested at a Manila airport early on Tuesday in a major step in the ICC's investigation into thousands of killings in an anti-drugs crackdown that caused shock and condemnation around the world.
"I am confident the arrest was proper, correct and followed all necessary legal procedures," President Ferdinand Marcos Jr told a news conference confirming Duterte had left the country bound for the Netherlands.
"We did not help the International Criminal Court in any way. The arrest was made in compliance with Interpol."
His daughter Sara Duterte, the Philippines' vice-president, boarded a morning flight to Amsterdam, her office said on Wednesday, but it did not what she intended to do there or how long she planned to stay in the Netherlands.
The "war on drugs" was Duterte's signature campaign platform that swept the mercurial crime-buster to power and he soon delivered on promises he made during vitriolic speeches to kill thousands of drug pushers and users.
Duterte has long insisted he instructed police to kill only in self-defence and has always defended the crackdown, repeatedly telling his supporters he was ready to "rot in jail" if it meant ridding the Philippines of drugs.
Veronica Duterte, the 79-year-old's youngest daughter, said on Instagram her father had boarded the jet but the family had not been informed of its destination.
"The airplane used to kidnap my dad just left minutes ago," she posted.
Hundreds of Duterte's supporters gathered outside the Villamor Air Base in Manila after learning the plane taking the ex-president to The Hague had left the airport.
Duterte's arrest follows years of him rebuking and taunting the ICC since he unilaterally withdrew the Philippines from the court's founding treaty in 2019 as it started looking into allegations of systematic murders of drug dealers on his watch.
The ICC, a court of last resort, is probing alleged crimes against humanity and says it has jurisdiction to investigate alleged crimes that took place while a country was a member.
Duterte and his family and allies expressed fury at the arrest, calling it unlawful.
A lawyer petitioned the Supreme Court on Duterte's behalf on Tuesday seeking a temporary restraining order to prevent authorities from complying with the ICC's request.
A copy of the warrant, seen by Reuters, said Duterte is accused of criminal responsibility for the murder of at least 43 people between 2011 and 2019, which would include time when he served as mayor of southern Davao City.
Human rights groups and families of victims said his detention was a key step towards accountability for the killings of thousands of people in the Philippines, where police investigations have moved at a snail's pace.
Duterte has not been charged with any crimes locally.
According to police, 6200 suspects were killed during anti-drug operations under Duterte's presidency that they say ended in shootouts.
But activists say the real toll of the crackdown was far greater, with many thousands more slum-land drug users, some named on community "watch lists", killed in mysterious circumstances.
The prosecutor of the ICC has said as many as 30,000 people might have been killed by police or unidentified individuals.
Police have rejected allegations from rights groups of systematic murders, staged crime scenes and fabricated incident reports.
