Firebrand Philippine President Rodrigo Duterte has lashed out with fresh obscenities at foreign critics of his deadly anti-drugs campaign, while issuing a veiled threat to potential coup plotters saying "we're watching you".

The man known as the "Punisher" told local government officials in his home-town of Davao that he became enraged after reading that the European Union had passed a resolution condemning extra-judicial killings in his island-nation of 100 million people.

"I told them 'f--- you. You are only doing it to atone for you own sins'," he said, raising his finger in an obscene gesture.

In another speech Mr Duterte said his foreign critics should know that under his campaign 700,000 drug pushers and users have surrendered to police.

"They [the critics] do not want a safe Philippines. They want it to be ruled by criminals. Oh, well, I'm sorry. That is you idiotic view," he said.

Earlier this month  the 71-year-old former mayor called US President Barack Obama the "son of a whore" ahead of a meeting of world leaders in Laos. Mr Obama swiftly called off a planned meeting between them as a result.

Swept into office in May pledging to wipe out drug dealers and criminals within months, police have since killed more than 1500 accused drug suspects, while another 1500 have been killed by unidentified assailants.

The pace of the killings is increasing as Mr Duterte insists there will be no let-up in the campaign.

Nineteen people, including a police officer, were killed on the streets of Manila between Monday and Tuesday evening this week.

The crackdown has broad support in the country with one of the highest rates of drug use and crime in Asia but has been widely condemned by human rights groups and some Western nations, including the United States.

Mr Duterte's brash unconventional style has also alienated many of the powerful families who have run the Philippines for decades.

His spokesman Martin Andanar said the new administration has identified people behind a plot to have the president removed from office by next year.

"We have names. We know who they are. We are studying it. The warning is – just be careful what you plan because it's against the law," he said.

The Philippine military staged six plots to overthrown former president Corazon Aquino between 1986 and 1987.

But since taking office Mr Duterte has promised to increase the pay of security service personnel and has often visited military bases to make patriotic speeches.

Mr Duterte has also been swift to attack his critics at home, including Leila de Lima, the chair of a Senate hearing that last week heard the evidence of a self-confessed hit-man who alleged the president had ordered killings when he was mayor of Davao.

But Mr Duterte's supporters in the Senate have stripped her of her post amid allegations she had received pay-offs from drugs lords.

Ms de Lima told the Senate she was the victim of a "new McCarthyism".

"Many friends and colleagues have told me, if I only I did not call out the president on the murderous consequences of his new war in drugs, and decided to be meek as a sheep, I would not be in this trouble," she said.

Ms de Lima has repeatedly denied receiving any money from drug dealers or allowing them special treatment in jail when she was justice minister.

"I am not the one giving a bad image to the country before the international media," she said in an apparent reference to Mr Duterte's image abroad.

A spokesman for former president Benigno Aquino called the attacks on Ms de Lima an "unprecedented, brazen power play" to silence her.

(SMH)