President Rodrigo Duterte castigated on Thursday the United Nations Commissioner for Human Rights for urging an investigation against him for allegedly being a murderer.

"There is this one United Nations official, human rights. He said Duterte is allegedly a murderer. He should be charged for murder. I should be investigated. This guy, I said is (either) a joker or insane," Duterte said in a speech in Pampanga.

UN High Commissioner Zeid Ra’ad Al Hussein called on Philippine judicial authorities to conduct an investigation against Duterte after he recently admitted killing people when he was mayor of Davao City .

Duterte said Al Hussein should study international law, citing the UN is an organization being subsidized by member countries, like the Philippines .

"You, officials… we pay your salaries. You, idiot, you do not tell me what to do. I am your employer. Do not do it to a nation. Who gave to you the right? You lack (knowledge) on international law?" he said.

"Do not talk like as if I am your employee. I am a member of a sovereign state. Please shut up... Idiot. Go back to school," Duterte said.

Duterte said Al Hussein should know diplomacy. "You do not talk to me like that. You, son of a bitch," he added.

Hussein's call for an investigation on Duterte was triggered by the president's recent admission that when he was mayor of Davao, he and policemen killed three suspected kidnappers.

“Such acts directly contravene the rights enshrined in Article III of the Philippine Constitution,” the UN official said.

"The killings described by President Duterte also violate international law, including the right to life, freedom from violence and force, due process and fair trial, equal protection before the law, and innocence until proven guilty. As a government official, if he encouraged others to follow his example, he may also have committed incitement to violence.”

“The Philippines judicial authorities must demonstrate their commitment to upholding the rule of law and their independence from the executive by launching a murder investigation,” Al Hussein said. Celerina Monte/ DMS