Philippine President Rodrigo Duterte has reacted angrily at the United Nation's human rights chief, Zeid Ra'ad al-Hussein, by calling him an "idiot" after the UN official urged the country's authorities to investigate the leader for murder.

"You there in the United Nations, you do not know diplomacy," Duterte is quoted to have said by the media.

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"You do not know how to behave, to be an employee of the United Nations. You do not talk to me like that, you son of a b*tch," Duterte continued in his remarks that were reportedly made to a gathering of civilian watchdogs.

In a statement released by the UN on Tuesday, al-Hussein said: "It should be unthinkable for any functioning judicial system not to launch investigative and judicial proceedings when someone has openly admitted being a killer."

Earlier this week, the Philippine Commission on Human Rights promised to investigate Duterte's boastful claims that he personally killed criminals.

The commission also plans to investigate Duterte on accusations that he was in charge of the so-called death squads that are said to have killed hundreds of people in Davao.

Last week, Duterte himself admitted to a British media house that he had personally killed at least 300 suspected criminals when he was mayor of Davao city.

Chito Gaston, the chairman of the rights body, however, told the media that president Duterte enjoys constitutional immunity as long as he is in office.

Since assuming power in June, Duterte has launched a bloody war on drugs, leaving an estimated 6,000 dealers dead at the hands of the police and vigilante groups.

Duterte has been ramping up verbal attacks on Western countries, including former ally the United States.

TagsRodrigo Duterte, United States, United Nations, Human Rights