Businessman Jee Ick-Joo was strangled to death in police headquarters in Manila in October a year ago - one of 7000 to be killed after Duterte called for the death of all people linked to the drug trade.
"We have to focus our effort toward internal cleansing and by the time we have cleansed the national police, the president will determine that and he will instruct us to go back to our war on drugs", said Dela Rosa, warning wrongdoers they face dire punishments.
A nongovernmental anti-crime group has documented at least 11 additional cases in recent months in which anti-drug police personnel are implicated "in procuring search warrants and instead of searching, they demand ransom from the victims".
Duterte has made the war on drugs a central tenet of his leadership - even claiming in December that he personally killed suspected criminals when he was mayor of Davao City.
Police may have committed crimes against humanity with these acts, the report said.
Police officers are paid as much as P15,000 for every drug suspect they kill, according to Amnesty International (AI).
AI-Philippines campaigner Wilnor Papa also railed against suggestions that the killings may be curbed by reimposing the death penalty.
The suspension dela Rosa said is to allow for Philippine investigators to purge police ranks with suspected links to the drug trade.
However Duterte emphasised repeatedly that the drug war would continue as long as he was in power, and he did not state that police would stop trying to eliminate drugs.
DAVAO CITY, Philippines-- A New York-based human rights organization said Tuesday that the United Nations should conduct an global investigation that would look into the killings in the Philippines amid announcement by the government to suspend its anti-illegal drug campaign.
Duterte, a firebrand lawyer, repeatedly told police during the election campaign and after assuming the presidency that he would shield them from prosecution if they killed people as part of the crime war. Police have classified most extrajudicial killings as "death under investigation". They earn about $100 for each drug user killed and $200 to $300 for each seller-from the police. They have also claimed that numerous deaths are caused by inter-gang drug violence caused by rising official pressure on their illicit trades.
Speaking on Monday, the head of the Philippines National Police Ronald dela Rosa said the president had told him to clean up the police force before resuming the crackdown.
"It never happens that there's a shootout and no one is killed", the officer said.
The PNP and Mr Duterte strongly reject claims that police have been involved in widespread extrajudicial killings. "They were still gunned down".
Speaking to newly promoted army generals, Duterte said he had sought China's help in unsafe waters in the south to check the activities of Abu Sayyaf, a Muslim rebel group sustained by piracy and kidnap-for-ransom activities. Police and government officials have denied the existence of bounty bonuses. "We have a problem", said Senator Panfilo Lacson, a former police director general. "The implication is that there might be impunity and [the police] are using the fight against illegal drugs for their self-aggrandizement".