Former Philippine President Rodrigo Duterte said he takes full responsibility for his administration's "war on drugs".

This was in a video message posted on his Facebook account, as he braces for a legal battle at the International Criminal Court.

"Whatever happened in the past, I will be the front of our law enforcement and the military. I said this already, that I will protect you, and I will be responsible for everything," Duterte said.

His remarks were his first since being put on a plane to The Hague.

Duterte was taken into custody by the ICC on Wednesday following his arrest in Manila on murder charges linked to his "war on drugs" in which thousands of purported dealers and users were killed.

The video, which has been viewed 10 million times, showed only Duterte speaking, while wearing a plain white shirt. It appeared to have been recorded inside the plane, with the faint hum of the engine audible in the background.

In a statement, the ICC said Duterte was "surrendered to the custody of the International Criminal Court. He was arrested by the authorities of the Republic of the Philippines...for charges of murder as a crime against humanity".

He will be brought before an ICC judge in The Hague in coming days for an initial appearance, the statement said. He was transferred to a detention unit on the Dutch coast.

"This will be a long legal proceeding, but I say to you, I will continue to serve my country. And so be it, if that is my destiny," Duterte said, while assuring his supporters he was well.

"I am okay, do not worry," the 79-year old former Philippine leader said in the more than two-minute video clip.

Duterte, who led the Philippines from 2016 to 2022 , will face allegations of crimes against humanity for overseeing death squads in his anti-drugs crackdown. He could become the first Asian former head of state to go on trial at the ICC.

The ICC arrest warrant says that as president, Duterte created, funded and armed the death squads that carried out murders of purported drug users and dealers.

During his six years in office, 6,200 suspects were killed during anti-drug operations, by the police's count.

Duterte's daughter, Sara Duterte, the Philippines' vice president, arrived in The Hague on Wednesday evening, her office said.

Lawyers and academics said the arrest and transfer were a big moment for the ICC, which is targeted by U.S. sanctions and does not have any police of its own to arrest people.

A State Department spokesperson said the United States is aware of Philippine authorities' arrest of Duterte.