Philippine President Rodrigo Duterte on Friday called the United Nations High Commissioner for Human Rights Zeid Ra’ad al-Hussein an “idiot” and a “joker”, Reuters reported. His comments came after al-Hussein on Tuesday had said the Philippines should investigate Duterte’s claims of personally killing people when he was the mayor of Davao city.

“This guy [Hussein] is ever the joker or crazy,” Duterte said according to Reuters, adding, “You idiot, do not tell me what to do ... Who gave you the right?” He further said the UN did not know what diplomacy was and said al-Hussein did not know how to behave as a UN employee and called him a “son of a bitch”, according to the news agency.

The UN official on Tuesday had said the killings would “clearly constitute murder”. “It should be unthinkable for any functioning judicial system not to launch investigative and judicial proceedings when someone has openly admitted being a killer,” al-Hussein had said.

On Sunday, the Philippine president, while visiting an army base in Zamboanga, threatened to set fire to the UN headquarters in New York, The New York Times reported. “You go and file a complaint in the UN...I will burn down the United Nations if you want. I will burn it down if I go to America,” he reportedly said.

In September, Duterte had used abusive language against outgoing President of the United States Barack Obama and had called him a “son of a bitch”.

Last week, Duterte had admitted that he had personally shot dead criminals. In 2015, he had said that he had killed three men involved in a kidnapping and rape case in the late 1980s. During his tenure as the mayor of Davao from 1988 to 2013, nearly 1,000 people were reportedly killed. More than 6,000 suspected drug dealers and users were said to be dead under his anti-drug campaign, which he started after becoming the president.

An independent rights watchdog, the Philippines Commission on Human Rights said it will also investigate the probe reports which claim that “death squads” killed several hundred people in Davao.