Rodrigo Duterte called a top UN official an "idiot" and "joker" for urging murder investigations be launched against him after the Philippines' president admitted to "personally" killing criminals while he was mayor of Davao City.

Zeid Ra'ad Al Hussein, UN High Commissioner for Human Rights, on Tuesday said Philippine judicial authorities should probe Duterte's accounts of having carried out killings.

"This guy [Zeid] is ever the joker or crazy," Duterte said during a televised speech on Thursday, and repeatedly called him "stupid".

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"You UN officials, sitting there on your asses, we pay you your salaries. You idiot, do not tell me what to do ... Who gave you the right?"  

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Duterte told businessmen last week that as mayor he killed criminals on the streets, and later admitted shooting dead three men involved in a kidnapping case during a police gunfight in the late 1980s.

Zeid said investigations should also be opened into deadly anti-drug campaigns in Davao when Duterte was mayor, as well as the "shocking" number of deaths during the current nationwide campaign.

More than 6,000 people have been killed as part of Duterte's crackdown, one third by police and the rest still officially under investigation. Duterte says the shootings by police were in self-defence.

"Please shut up because your brain is lacking there," he told Zeid. "Go back to school. You United Nations, you do not know diplomacy. 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 bitch," he added.

Independent watchdog probe

Meanwhile, the Philippines' independent rights watchdog said on Thursday it will investigate Duterte's boasts that he killed criminals years ago. Philippine Commission on Human Rights chief Jose Gascon said he had formed a team of investigators to look into the alleged killings.

"Law enforcement agencies ... must investigate as a matter of course any information that suggests that a crime may have been committed with the view to ensuring that perpetrators are ultimately held accountable -should the evidence warrant it," Gascon said in a statement.

Duterte also on Thursday threatened to "whack" the Philippines' money laundering council, a regulatory body headed by the central bank governor, accusing its officials of corruption and failing to do their job.

The Philippines president, who is given to incendiary language, demanded that members of the central bank's Anti-Money Laundering Council resign for failing to provide him an unspecified "assessment report".

"I'll count one to three and if you don't resign, I will treat you as a drug addict," he said.

"Better prepare there because I'll give you a whack. But you are all, you are all corrupt," he said in a speech after signing the 2017 national budget.

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Source: News agencies