MANILA - Most Filipinos support greater scrutiny by international groups of the Philippines' drug war.

Three out of five respondents in a survey by reputable polling firm Social Weather Stations said the government should not block investigators from the United Nations and other advocacy groups abroad from looking into the thousands of deaths since President Rodrigo Duterte began a brutal crackdown on the narcotics trade in mid-2016.

The UN's top human rights body on July 11 passed a resolution, presented by Iceland, calling for a probe into these killings.

The resolution called on the Philippines to "take all necessary measures to prevent extrajudicial killings and enforced disappearances".

It also sought a written report on the Philippines for consideration at the Human Rights Council's summer session next year.

The Philippines has rejected the resolution.

"(We) cannot, in good conscience, abide by it. We will not accept a politically partisan and one-sided resolution, so detached from the truth on the ground," Foreign Affairs Secretary Teodoro Locsin said soon after the resolution was approved.

Interior Secretary Eduardo Ano, a former military chief, insisted in a news briefing on Tuesday (July 23) that the Philippines had "enough systems, courts processes… to make sure that we will come up with an honest report, and we will do that".

He said it would be a "violation of our sovereignty" if the government were to allow "a foreign entity" to investigate a domestic issue.

Mr Ano added that the UN and other groups seeking to investigate the drug war had facts that were "very different from the facts we have".

"How can you allow somebody to investigate without even verifying the source of this information? This is really a flagrant violation of our sovereignty," he said.

Human rights groups claim tens of thousands are being killed, as police terrorise poor communities using cursory drug "watch lists" to identify suspected users and dealers, and executing many of them under the guise of sting operations.

The government rejects that as lies, and say those killed were armed and resisted arrest.

It also insists that only about 5,400 drug suspects have died since 2016, far lower than the over 25,000 that activists are presenting to the UN.

Amnesty International has described the drug war as a "large-scale murdering enterprise for which the poor continue to pay the highest price", and that it has reached "the threshold of crimes against humanity".

The International Criminal Court is itself examining whether the thousands of killings that resulted from Mr Duterte's war are sufficient to warrant a formal investigation into possible crimes against humanity.

In his annual address to Congress on Monday, Mr Duterte vowed to step up his drug war, as he pressed lawmakers to reinstate the death penalty.

Mr Duterte lamented that halfway through his six-year term, the drug problem had worsened.

He had promised to eradicate the drug menace in six months when he ran for president in 2016. But he has since conceded that the problem was bigger and more complex than he had anticipated.

"I am aware that we still have a long way to go in our fight against this social menace," he said.