MANILA (Reuters) - Philippine President Rodrigo Duterte has ordered police to halt activities in his deadly war on drugs and leave all operations to the drug enforcement agency, amid unprecedented scrutiny of police conduct.

President Rodrigo Duterte speaks before members of the Australian Navy during a tour on board the the Royal Australian Navy (RAN) vessel, Her Majesty's Australian Ship (HMAS) Adelaide III upon arrival for a goodwill visit as part of the Australian Defence Force (ADF) Joint Task Group Indo-Pacific Endeavour 2017 at the Pier 15, south harbor in metro Manila, Philippines October 10, 2017. REUTERS/Romeo Ranoco

Duterte’s office on Wednesday made public a memorandum telling police, the military and other state bodies to leave to the Philippine Drug Enforcement Agency (PDEA) “as sole agency” the conduct of all campaigns and operations.

It was unclear why Duterte had ordered the change in the role of the police, who have been responsible for the vast majority of arrests and killings in the 15-month-old campaign.

Neither the presidential spokesman nor the communications secretary immediately responded to Reuters’ requests for comment.

The order could blunt the intensity of the crackdown, since the drug enforcement agency has only a fraction of the manpower of the 190,000-strong police. But it was not the first time the mercurial leader has decreed that the agency lead the drugs war.

Duterte suspended police anti-drugs operations in late January, to cleanse a force he called “corrupt to the core”, but lifted that ban five weeks later, saying drugs were flooding back to the streets and the gains of the war were being lost.

The memorandum, signed on Tuesday, ordered the police force at all times to “maintain police visibility, as a deterrent to illegal activities”, while restricting operations to the drug agency.

Its aim was “to bring order to the operation or campaign against illegal drugs, thus pinpointing precise accountability”, the document said.

More than 3,900 Filipinos have been killed in what the police called self-defense after armed suspects resisted arrest. Critics dispute that and say executions are taking place, with zero accountability, allegations the police reject.

Police and drug enforcement agency spokesman said the two agencies would follow the president’s decision, but did not elaborate.

Duterte’s move follows the August killing of a teenager by police that sparked rare public outrage after a security camera showed the victim in custody, contrary to a police report that he was a drug dealer who tried to shoot them.

It also follows a protest against Duterte last month by thousands of people in Manila, and a series of opinion polls highlighting doubts among many Filipinos about official police accounts, and whether those killed were all drug dealers.

A poll released on Sunday showed a sharp decline in public opinion about Duterte’s performance and personality, though sentiment about him remained positive overall.

Rights lawyers on Wednesday approached the Supreme Court to try and stop the war on drugs, saying it was illegal and allowed the police to circumvent legal procedure.