The Philippine police resumed their anti-narcotics operations yesterday with a promise that this new phase in President Rodrigo Duterte's controversial war on drugs will be "less bloody, if not bloodless".

Addressing hundreds of officers, police chief Ronald Dela Rosa said the 160,000-strong police force was reforming and called on "men of burning desire" to join a new task force, the Philippine Drugs Enforcement Group.

Mr Dela Rosa gave no details about this task force, except to say that it would go after "high-value targets" rather than the petty drug dealers and addicts who have made up the bulk of the more than 6,500 killed since Mr Duterte took office in June last year and launched a brutal crackdown on the narcotics trade.

"The war on drugs is on, and this time, it is going to be more extensive, aggressive and well-coordinated, with built-in systems that guarantee full accountability and instil internal discipline among all personnel," said Mr Dela Rosa.

"I hope that this will be less bloody, if not bloodless... Men of burning desire, you can report to the drug enforcement group. You can volunteer to join the war, with a burning desire to help in this campaign, to help this country."

Mr Duterte suspended all police drug operations on Jan 30 after rogue drug squad officers were found to have kidnapped and murdered a South Korean businessman.

The President described the police force as "rotten to the core" and ordered an "internal cleansing" before letting it return to the drug front lines.

But last week, he instructed Mr Dela Rosa to form smaller units consisting of "men imbued with the fervour of patriotism" to return to the campaign because drugs were back on the streets and he had insufficient manpower.

"It only goes to show that we cannot afford to lower our guard when confronting a vicious enemy. There must be continuity of effort if the desire is to completely eradicate the problem," said Mr Dela Rosa.

Mr Duterte's drug war continues to be popular in the Philippines, but critics have raised alarm over the unabated killings.

Amnesty International said last month that Mr Duterte has created incentives to kill and "an economy of murder", and that the mass killings may constitute a "crime against humanity".

The President responded by saying that "criminals have no humanity" and called Amnesty "naive and stupid".

In its annual human rights report, the US State Department last week took note of the killings and "cases of apparent government disregard for human rights and due process".

Mr Duterte's spokesman said in response that it was important not to link reports of abuses to the anti-drugs campaign, which was a "noble crusade".