MANILA, Philippines -- The Philippine president said Thursday he will invite the UN chief and European Union officials to investigate his bloody anti-drug crackdown, but only if he can question them in public afterward to prove their human rights concerns are baseless.

President Rodrigo Duterte disclosed the offer in a speech in which he again lashed out at critics of his crackdown, including President Barack Obama and European countries. He accused them of hypocrisy for raising concerns about his anti-crime fight while launching military strikes that have killed innocent people in the Middle East.

The tough-talking former city mayor cited the recent shooting to death of a black man in the U.S. and the involvement of European countries in military actions in the Middle East.

After the European Parliament called for an end to the drug killings and expressed concern over the scale of deaths, Duterte hit back earlier this week with a profane insult and raised a fist with his middle finger thrust out.

"I will write them a letter to invite them for an investigation but, in keeping with the time-honoured principle of the right to be heard, after they've grilled me, I'll also question them," Duterte said in a speech in southern Misamis Oriental province.

"Everybody would be invited," he said of his public questioning of his critics. "Just watch how I will scrub down those demons."

Turning to America, he asked, "What if I deploy a rapporteur to America and ask why the blacks there were being shot?"

More than 3,000 suspected drug dealers and users have been killed since July and more than 600,000 others have surrendered for fear of being killed in Duterte's crackdown. Despite growing alarm, Duterte said he won't stop the campaign.

Duterte also hit out at a vocal critic of his anti-drug war, Sen. Leila de Lima, whom he has accused of involvement in the illegal drug trade through a former driver who allegedly used her influence to collect payoffs from detained drug lords.

De Lima has denied any wrongdoing and said in a news conference Thursday that she feared for her life. She denounced the disclosure of her cellphone number in a congressional inquiry led by Duterte's allies on the drug problem in the national penitentiary, where drug lords are alleged to have helped finance her senatorial campaign.

"I'm now a subject of persecution and I'm no longer safe," de Lima said. "Can I rely on the regular authorities in government?"

The 71-year-old Duterte overwhelmingly won election in May on an audacious promise to eradicate corruption and crime, particularly illegal drugs, in six months. He recently said he underestimated the magnitude of the drug problem and will extend the crackdown by another half year.

"Even if I wanted to, I cannot kill them all because the last report would be this thick," Duterte said this week, displaying a new police list of drug suspects that he said includes many village chieftains, town mayors and provincial governors.