The United Nations has said Philippine President Rodrigo Duterte has a "striking lack of understanding" of its human rights institutions in a rebuke over his crime war that has killed more than 3,000 people. The fresh criticism came from UN rights chief Zeid Ra'ad Al Hussein after Duterte called UN head Ban Ki-moon a "fool" and threatened to pull out of the organization in response to the global body's condemnation of alleged extrajudicial killings in his anti-drug campaign. The sharp-tongued Duterte has said he does not "give a shit" about a wave of international criticism, including from the UN and US President Barack Obama. "The President of the Philippines's statements of scorn for international human rights law display a striking lack of understanding of our human rights institutions and the principles which keep societies safe," Zeid said at a speech in Geneva on Tuesday. Duterte, 71, has launched an unprecedented crime war since taking office on June 30, warning the Philippines is in danger of becoming a "narco-state." He was elected in a landslide in May after pledging to kill 100,000 criminals and promising to protect police from prosecution if they are charged over the deaths. Last month, Duterte announced a "shoot-to-kill" order against drug dealers. "This campaign (of) shoot-to-kill will remain until the last day of my term if I'm still alive by then," he said. Zeid said such an order "undermines justice." But on Wednesday, Philippine Ambassador to the UN Cecilia Rebong said Duterte never empowered police to shoot to kill anyone. "What he said was the police have the right to defend themselves when their lives are in danger," Rebong told the UN Human Rights Council. Duterte's spokesman Ernesto Abella added that Duterte did not tolerate extrajudicial killings but that "human rights cannot be used as an excuse to let the spread of drugs in the country run rampant." Police reported on Wednesday killing 1,506 people in anti-drug operations in just over two months since Duterte took office. Another 1,715 were classified as "deaths under investigation," referring to people killed in suspicious circumstances including those shot by suspected vigilantes or found dead with crude cardboard signs labeling them as drug traffickers. Zeid urged the Philippines to invite a UN human rights expert to investigate the killings. Philippine foreign affairs spokesman Charles Jose was non-committal, saying UN rights experts already "jumped to conclusions." Duterte last month lashed out at UN special rapporteur on summary executions Agnes Callamard for saying his directives amounted to an international crime.