An Amnesty report, which followed an in-depth investigation into the drug war, also outlined what it said were other widespread police crimes aside from extrajudicial killings that mainly targeted the poor.
"Acting on orders from the very top, policemen and unknown killers have been targeting anybody remotely suspected of using of selling drugs," Rawya Rageh, a senior crisis adviser for Amnesty, told AFP.
"Our investigation shows that this wave of extrajudicial killings has been widespread, deliberate and systematic, and therefore may amount to crimes against humanity."
It also said police were being paid by their superiors to kill, and documented victims as young as eight years old.
Also Read
"The police are behaving like the criminal underworld that they are supposed to be enforcing the law against," the report said.
Duterte won presidential elections last year after promising during the campaign to eradicate drugs in society within six months by killing tens of thousands of people.
Duterte launched his crackdown immediately upon taking office seven months ago.
Since then, police have reported killing 2,555 people while nearly 4,000 others have died in unexplained circumstances, according to official figures.
As president, Duterte has repeatedly urged police to kill drug users as well as traffickers.
Duterte said in December he had personally killed people when he was mayor of a southern city to set an example for police.
The Amnesty report said Duterte had incited the police to carry out a murderous war on the poor, and warned that the International Criminal Court would need to start investigating unless Philippine authorities did not stop it soon.
Disclaimer: No Business Standard Journalist was involved in creation of this content