The Philippine police yesterday suspended President Rodrigo Duterte's bloody war on drugs, as it refocuses its efforts on purging its ranks of rogue officers.

The move comes as the 160,000-strong Philippine National Police (PNP) is shaken by a scandal over the kidnapping and slaying last year of a South Korean man, allegedly by anti-narcotics officers.

"There is no war on drugs for the meantime. We're shifting to a war on scalawags. We will clean our own ranks first. Then after that, maybe, we can resume the war on drugs," director-general Ronald de la Rosa, the PNP chief, told reporters.

Hours earlier, at a late evening news conference on Sunday, Mr Duterte ordered the PNP to disband its anti-illegal drugs group, and all precinct-level anti-narcotics units.

"Something has to be corrected severely… Let me reorganise the system," he said, describing the police force as "the most corrupt".

"You are corrupt to the core. It's in your system," the President said, suggesting that two in five policemen are probably tainted.

Mr de la Rosa had offered to resign, but Mr Duterte said: "What good will come of it? You can't be blamed for this." Mr de la Rosa was police chief when Mr Duterte was mayor of the southern city of Davao.

The "internal cleansing" of the police force arose from a discovery that errant cops were behind the abduction and murder of Mr Jee Ick Joo, a South Korean businessman.

Mr Jee was seized in October by an anti-narcotics team, under the pretence of a drug raid. He was taken to a compound inside the camp housing the headquarters of the PNP's top brass in Manila. While there, and just steps away from Mr de la Rosa's office, police officer Ricky Santa Isabel strangled Mr Jee.

Santa Isabel then demanded a ransom of five million pesos (S$143,300) from Mr Jee's wife. Not knowing Mr Jee was already dead, she paid on Oct 31. But Santa Isabel then asked for another four million pesos.

During a Senate hearing last week, Santa Isabel tagged his supervisor Rafael Dumlao as the "brains" behind the kidnapping and slaying.

On Sunday, Mr Duterte offered a five million peso reward for Dumlao's arrest, "dead or alive".

"You deliver him to me dead, I'm okay with that… (Dumlao) put the reputation of the police in shambles," he said.

Mr de la Rosa afterwards informed Mr Duterte that Dumlao was already in police custody, and that Dumlao had confessed to the crime.

Mr de la Rosa said he does not know how long the police purge will last. He said he will form a "counter-intelligence task force" to go after errant cops, and a new "narcotics command" may be set up later.

Mr Duterte, meanwhile, said his crackdown on illegal drugs will continue until the end of his term in 2022.

"I will extend it to the last day of my term. March no longer applies," he said.

He had promised during his campaign to rid the Philippines of the "drug menace" in six months. He later asked for three more months, saying he was unaware, until he assumed office, how widespread the problem had become.

Critics questioned the sincerity of the police "cleansing".

Mr Phelim Kine, deputy Asia director at Human Rights Watch, said "it is nothing less than an empty public relations gesture".

Mr Renato Reyes, secretary-general of Bayan (Nation), a coalition of leftist activist groups, said: "How can a corrupt and fascist police force, where impunity is the norm, successfully stamp out criminal activities such as the illegal drug trade? The body count will continue to rise and more criminals in uniform will wreak havoc on the people."

SEE WORLD: Duterte accuses US of building arms depots