The crackdown, however, has spawned wider violence and thousands of killings, with near-nightly attacks taking place mostly in slums and often at the hands of vigilantes, human rights groups said.
"If there are cases of killings in your parish community, I ask our pastors and lay leaders to take time to go to the wake in order to bless the departed and to be one with the grieving families in sorrow and in hope", Tagle said.
"These killings demonstrate that Duterte's rejection of the rule of law has made all Filipinos potential "drug-war" victims, no matter how young", Kine said.
Amnesty International said the three teenagers were among more than 50 children killed in a wave of extra-judicial killings in the Philippines since Duterte came into office and launched the drug war.
"One major issue our esteemed lawmakers shall have to deliberate is whether it's better to continue current efforts to regain what rightfully belongs to the government now going on for 31 years or to negotiate a settlement that would obtain billions of pesos for the nation's use now", he said.
He added: "That's illegal and I won't tolerate it. Watch out. Someone's cooking out there somewhere to discredit us", he said. "Now if you are an authority, you have gone overboard", he said.
Arnaiz's body was identified 10 days later in a morgue in Caloocan City.
Duterte's drug war remains hugely popular among a citizenry fed up with high crime, according to many surveys. Witness statements and CCTV footage support this claim.
It set back what was a promising revival of the long-stalled peace negotiations after Duterte vowed to achieve peace across all fronts, including with Moro rebels, at the start of his term.
Anger and protests have focused on the killing of Delos Santos, who police claimed was a drug dealer who opened fire with a pistol during a raid. "That is murder", Duterte said in mid-August, following the controversial death of de los Santos.
Arnaiz's parents were also summoned to Malacañang earlier this week and Duterte also assured them that their son's death will be given justice.
Kine also slammed plans for the mandatory drug testing of all college students and applicants, saying this would "effectively allow the police to extend their abusive anti-drug operations to college and university campuses, placing students at grave risk". "But if they have no gun, give them a gun".
As a former prosecutor, Duterte said he knows how the police officer should behave in arresting a suspect. He was allegedly involved in a shootout with police officers who tried to arrest him after he was accused of robbing a taxi driver, a police report said.