Amnesty International has accused the Philippine police of "systematically planning" extrajudicial killings in the controversial war against drugs.
The rights group also said in a report that the killings may constitute "crimes against humanity".
More than 7,000 have been killed since President Rodrigo Duterte launched his "war" on the drug trade in July.
He has always defended the crackdown, saying police were only authorised to open fire when threatened by suspects.
But on Monday, the president suspended it and ordered a "clean-up" of the police force following the murder of a South Korean businessman by a group of rogue anti-drug police officers.
There has been no government reaction to the Amnesty report, but the Philippine police have also consistently said those killed were resisting arrest.
Amnesty disputed this based on witness testimony and independent investigations, saying it was "deeply concerned that the deliberate and widespread killings of alleged drug offenders....appear to be systematic, planned and organised by the authorities".
"Police officers routinely bust down doors in the middle of the night and then kill in cold blood unarmed people suspected of using or selling drugs.
"In several cases documented by Amnesty International, witnesses described alleged drug offenders yelling they would surrender, at times while on their knees or in another compliant position. They were still gunned down."
Amnesty also said officers planted evidence and falsified reports to "cover their tracks".
The rights group said there appeared to be financial incentives for the killings, with one officer claiming they were given an "under the table" payment for each death, as well as payments from some funeral homes.
The rights group said the vast majority of those killed were poor and on "drug watch lists" prepared by government officials and shared with police.
It said the lists were "deeply problematic" and that names could be put on it "based on hearsay and community rumour or rivalry, with little to no verification".
The group spoke to 110 people for the report including witnesses of killings, victims' relatives, drug users, police officers, and members of government, civil society and religious groups.
Mr Duterte has come under heavy criticism from rights groups and Western countries for his hardline stance on drugs.
But the shocking and high-profile kidnap and murder of the South Korean businessman prompted Mr Duterte to admit that the police is "corrupt to the core" and he suspended the drug war with all anti-drug units dissolved and ordered a re-organisation of their ranks.
He has in the past sanctioned extra-judicial killings by the police, saying he would pardon them for such acts, and once said he would be "happy to slaughter" three million drug addicts.