Duterte on Monday suspended police from anti-narcotics operations after a South Korean businessman was murdered by rogue drugs squad police.
He has put the Philippine Drug Enforcement Agency (PDEA) in charge, and plans to deploy troops as reinforcements.
Duterte said his campaign was about destroying the apparatus of the drugs trade, not killing, and only he would be accountable if law enforcers were accused of wrongful killings during raids and sting operations.
“Those done in the line of duty I take full responsibility,” he said.
“If someone should go to jail, it’s not police, not military, not the PDEA, It’s me.”
Duterte’s war on drugs has attracted global attention due to its high death toll in his first seven months in office and the shock factor of images in media of bloodied corpses lying in streets and slums.
As at Jan. 31, some 2,555 Filipinos were killed in what police said were shootouts during anti-drugs operations.
More than 7,700 deaths have been recorded overall, and the cause of many of those are much in dispute.
The Catholic Church used sermons at the weekend to speak out about the drugs war, saying killings were not the solution and the poor were being worst hit.
A Feb. 1 report by Amnesty International said the same, and concluded that police had behaved like the criminal underworld they were supposed to suppress, taking payments for killings.
The report said many killings were “systematic, planned and organised” by authorities.
Duterte rubbished those claims and said it was necessary to provide undercover police with cash to buy drugs in sting operations, referred to as “buy-busts”, otherwise prosecuting dealers would be difficult.
He denied his campaign was focusing on small-time users and pushers only, and he had proved local politicians were on his radar.
“There is always a contention Duterte is killing the poor,” he said.
“So where is the big fish? We started with the mayors, they were killed along the way, so there’s the big fish,” he said.
In Tuesday’s New York Times, Gaviria, who was Colombia’s president from 1990-1994, appealed to Duterte to use alternative strategies to fight drugs and explained why his country’s crackdowns on cocaine cartels had failed.
He hoped Duterte would avoid a heavy-handed approach and “not fall into the same trap”.
“Trust me, I learned the hard way,” he wrote.
Duterte said Gaviria was “lecturing” and the Philippine case was different to Colombia, because “shabu”, or methamphetamine, was damaging to the brain whereas the behavioural impact of cocaine was less severe.