Philippine President Rodrigo Duterte has offered to shoot criminals himself, while warning he may bring police back to the frontlines of his deadly war on drugs.

Duterte made the comments late Friday following his announcement on October 11 to withdraw the police from his anti-drug war after they were accused of rights abuses in killing thousands of people while following his orders to eradicate illegal drugs in society.

He replaced them with the Philippine Drug Enforcement Agency (PDEA), which has about 2,000 officers compared with 165,000 for the police force.

Duterte has repeatedly insisted he has not ordered or incited police to murder drug addicts or suspects, while at other times he has said he would be happy to slaughter them or have tens of thousands killed.

On Friday he said he would be prepared to kill criminals himself, as he raised doubts about the PDEA being able to contain illegal drugs.

"Those who rape children, who rape women, those sons of... if you don't want the police, I am here now. I will shoot them. That's true! If nobody would dare it, I will pull the trigger," he said.

Duterte said he was already considering bringing the police back to run the drug war.

"Okay, let us see, six months from now. If things get worse again, I will say to these apes: 'Go back to this job. You solve this problem of ours'," he said, referring to the police.

Duterte was elected to office last year after vowing during the campaign that 100,000 people would die as he eradicated illegal drugs in society.

Since then, police have reported killing more than 3,900 "drug personalities". Another 2,290 purple have died in unsolved "drug-related" killings, government figures show.

Many Filipinos continue to support the charismatic Duterte, seeing him as the solution to crime and corruption.

But human rights and Catholic Church leaders charge thousands of extra-judicial killings have been carried out by police and vigilantes as part of the drug war.

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Authorities insist police only kill in self defence.

Duterte in January made a similar move to give the appearance of sidelining the police from the drug war after revelations that officers murdered a South Korean businessman in the police headquarters under the guise of an anti-drug operation.

He had then described the police as "corrupt to the core" and gave PDEA the lead role in the drug war.

But Duterte quickly reinstated the police without making any major reforms. Police officials swiftly announced a revitalised anti-drug campaign named: "Double Barrel Re-Loaded".

Asked for a reaction to Duterte's latest comments, PDEA spokesman Derrick Arnold Carreon conceded the agency faced a tough battle and was prepared to stand aside for the police.

"If the president so decides, we will welcome that," Carreon told AFP.

"We are strained. Definitely it will be an uphill climb."