The United Nations High Commissioner for Human Rights has slammed President Rodrigo Duterte for "empowering" law enforcers to shoot to kill drug suspects, with or without evidence, as this undermines justice.

In the opening of the 33rd session of the Human Rights Council on Tuesday in Geneva, High Commissioner Zeid Ra’ad Al Hussein included the Philippines as among those countries which his office has concerns over human rights issues.

"The President of the Philippines' 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," Al Hussein said.

He noted that fair and impartial rule of law is the foundation of public confidence and security.

"Empowering police forces to shoot to kill any individual whom they claim to suspect of drug crimes, with or without evidence, undermines justice," he said.

"The people of the Philippines have a right to judicial institutions that are impartial, and operate under due process guarantees; and they have a right to a police force that serves justice," the UN official stressed.

Al Hussein said he "strongly encourage" the Philippines to extend an invitation to the Special Rapporteur on extrajudicial, summary or arbitrary executions.

Duterte’s war on drugs, according to estimates, has left nearly 3,000 suspected drug pushers and users dead, with a little over half of them due to vigilante killings, two months since he took his oath of office.

It has raised concerns among human rights advocates, the UN and even Manila's long-time ally, the United States

He said his office is ready to assist, including with respect to rule of law institutions and the prevention and treatment of drug use in accordance with international norms. Celerina Monte/DMS