President Rodrigo Duterte on Saturday threatened United Nations special rapporteurs that they will be fed to crocodiles once they come to the country to investigate his administration's anti-drug war campaign.

During his speech in Zamboanga City, Duterte lashed out at UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein's statement against his order to the Philippine National Police to ignore any UN human rights investigation.

"They will go here. Are there crocodiles here? One who eats people? Throw them (there)," he said.

"This chief of (UN Human Rights Council).. they were angry because my advice (to authorities) is, 'Do not answer questions from them. And that is for a reason, legal. That is provided for in the Constitution itself, our Constitution," Duterte added.

He said his directive has legal basis and is provided for by the 1987 Constitution.

Duterte reiterated his order to the police to keep their silence, as he said responding to any questions might implicate them.

"The rule on criminal law is any statement or answer that you will give might incriminate you. If you said something when they hound you with questions, and you're free-wheeling (to answer), and they record it. You are bound (to pay) for everything you say when they summon you," he explained.

"So the best way is to give silence. There's a commander-in-chief. I told you already, I take full responsibility. Just do your job in the performance of your duty within the bounds of the law," he added.

Duterte also assured them he would take full responsibility as long as the members of the Philippine National Police are fulfilling their mandate. Ella Dionisio/DMS