President Rodrigo Duterte on Wednesday went on the offensive against critics of his bloody anti-drug campaign, slamming the United Nations for interfering in the country's internal affairs.

Duterte criticized the UN during the 115th police service anniversary of the Philippine National Police Wednesday afternoon, addressing the complaints about the high death toll in his anti-drug war which human rights groups claim are about 1,000.

"You know it’s very easy to complain. We in government and I myself who ordered the campaign against drugs take full responsibility for it and for those who are killed in a police operation and a firefight, we are willing to submit ourselves for an investigation before any body,” he said.

Duterte said 1,000 fatalities is a small figure compared to other casualties in armed conflicts in other parts of the world.

"And here comes the UN easily swayed and coming on a very stupid proposition of,

you know, for those who are killed by the drug syndicates. We can only investigate, but do not attribute acts of other criminals upon my government," he said.

Duterte went on a tirade against a senator for alleged politicking at the expense of the campaign to rid of the country of illegal drugs. The national police and other law enforcement officials will face the Senate on Monday for a hearing on extrajudicial killings.

Meanwhile, Philippine National Police Director General Ronald de la Rosa said the police directors of the National Capitol Region, central Visayas and the Bicol region will have to boost their efforts to combat illegal drugs or will be relieved.

The three are Chief Superintendent Oscar Albayalde of the National Capital Region Police Office, Chief Superintendent Jose Gentilles of central Visayas regional police and Chief Superintendent Melvin Ramon Buenafe of the Bicol regional police.

Dela Rosa's assessment was the result of a conference in Camp Crame on Monday where commanders of the 18 regional police offices submitted their reports.

"They have to up their tempo and their efforts. Otherwise, I will relieve them if they cannot measure up to our expectations," De la Rosa told reporters during an ambush interview on Wednesday. Emmanuel Tupas/DMS