The Philippines criticised on Tuesday as "irresponsible and alarming" a UN envoy`s warning that life sentences meted out to two ex-Khmer Rouge leaders should serve as a warning to Manila over human rights abuses.
Last week, a United Nations-backed court in Cambodia upheld life sentences for crimes against humanity for two senior leaders of the Khmer Rouge regime, which was responsible for the death of up to two million Cambodians from 1975-1979.
David Scheffer, the UN Secretary-General`s envoy to the tribunal, said leaders in countries such as the Philippines, as well as the Islamic State (IS) group, must "take note" of the verdict.
"Mr Scheffer`s remarks are irresponsible and alarming since these are directed at the leadership of a democratic country with a functioning criminal justice system," the Philippine foreign ministry said in a rare statement.
"His remarks are unjustified and without basis."
President Rodrigo Duterte, 71, has drawn a wave of international criticism for his drug war that has left more than 4,800 people dead.
The UN, the United States and the European Union have warned against alleged extrajudicial killings and a breakdown in the rule of law.
Duterte won May elections by a landslide after vowing to kill 100,000 criminals and rid the country of illegal drugs in six months.
Since he took office in June, 1,900 have died in police operations and another 2,900 were killed in unexplained circumstances, according to official figures.
After the verdict in Cambodia last week, Scheffer said the decision showed world leaders can be held accountable for atrocities.
"Leaders in the Philippines or in South Sudan or in Sudan or in the Central African Republic or in Syria or among (IS) in Syria and Iraq should all take note that what happened on Tuesday in this courtroom ultimately can reach their domain because international justice is not backing down."
He added: "Holding senior leaders accountable for the perpetration of atrocity crimes under their leadership, does happen, it does ultimately occur."
While Scheffer did not mention Duterte`s drug war, the Philippine foreign ministry defended the anti-crime crackdown.
"The government`s campaign against crime and corruption is being waged precisely for the protection of its people and the continued enjoyment of their rights," it said.
Duterte has been defiant following global criticism of his drug war and on Monday continued his verbal assault on critics.
He has threatened to follow in Russia`s footsteps and pull his country out of the International Criminal Court, the world`s only permanent war crimes court, in fury at foreign criticism of his deadly drug war.
The ICC`s chief prosecutor said last month she was "deeply concerned" about the Philippine killings.
"Do not believe those European lawyers. They are all stupid, believe me," he said Monday, adding they had brains "just like a pea".
He added: "You threaten me that you will jail me? International Criminal Court, bullshit."