Philippine President Rodrigo Duterte on Tuesday threatened to kill corrupt police, including those accused of involvement in illegal drugs and other crimes, in an expletives-laden encounter on live TV.

More than 100 police officers, many of them facing administrative and criminal complaints including rape, kidnapping and robbery, were escorted to the presidential palace to meet Duterte, police officials said.

The national police force, which Duterte once called "corrupt to the core," has been undergoing an internal cleansing since being removed twice from the president's crackdown on illegal drugs last year due to reports of abuses. Duterte later allowed them to rejoin drug raids, partly because the small lead anti-narcotics agency lacks personnel and firepower to quell the drug menace.

"If you'll stay like this, son of a bitch, I will really kill you," Duterte told the policemen in the dressing-down broadcast by local TV networks.

The cases of some of the officers will be reviewed, but Duterte warned, "I have a special unit which will watch you for life and if you commit even a small mistake, I'll ask that you be killed."

Protesters in Manila paint mock chalk outlines depicting those killed in the government's drug war during a protest on July 23. (Jes Aznar/Getty Images)

Addressing the policemen's families, Duterte said, "If these sons of bitches die, don't come to us yelling 'human rights, due process' because I warned you already."

Such public threats, along with the more than 4,500 mostly poor drug suspects who have been killed in gun battles with police under Duterte's anti-drug crackdown, have triggered alarm by Western governments and human rights watchdogs since he rose to power in mid-2016.

Duterte has vowed to press his campaign until the last day of his six-year term, often declaring that he is ready to go to jail, although he denies sanctioning extrajudicial killings. Police say nearly 150,000 drug suspects have been arrested and dozens of law enforcers have been killed in drug raids, proving the danger of battling illegal drugs, which remain a major problem.

The Bureau of Customs and anti-drugs authorities announced Tuesday night the discovery of about 1,100 pounds of methamphetamine, locally called shabu, concealed in two steel cylinders in two abandoned container vans at Manila's international container port in one of the largest drug seizures under Duterte.

Philippine Drug Enforcement Agency chief Aaron Aquino said the vans came from Malaysia, which a drug syndicate may be using as a trans-shipment point, but were never claimed at the Manila port because of stricter screenings.

Customs commissioner Isidro Lapena warned that customs personnel linked to drug traffickers would eventually be arrested. "The fact that this did not get through this time is an indication that many no longer want to co-operate with the drug syndicates," he told reporters.