Philippines President Rodrigo Duterte on Monday promised rewards running to tens of thousands of dollars for information leading to the capture of police officers protecting drug syndicates and warned corrupt officials they would face "a day of reckoning".

In a National Heroes Day speech, Duterte said there would be no let-up in a "war on drugs" in which - according to police figures - more than 1,900 people have been killed since he came to power two months ago.

Police say the toll of about 36 people a day is a result of drug dealers resisting arrest or gang feuds.

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Duterte railed against critics who have complained that the poor who trade drugs to make a living are being targeted by the police, but added that army generals, city mayors, governors and police involved in the drug trade must also be stopped.

"I consider the fight against drugs a war, there is a crisis in this country, it is drugs ... it has infected every nook and corner," he said in the speech to retired and serving soldiers, government officials and foreign diplomats.

Singling out corrupt policemen known as "ninjas", who take pay-offs from drug lords, Duterte said he was placing a 2 million peso ($43,000) bounty on their heads, telling their colleagues to "squeal on your friends".

Duterte, who won a May election on a promise to wipe out drugs and dealers, last month named about 160 officials, judges, police and soldiers who he said were protecting drug traffickers or selling drugs in their communities.

The United States, a close ally of the Philippines, said last week it was "deeply concerned" about the reports of extra-judicial drug killings and it urged Duterte's government to ensure that law-enforcement efforts "comply with its human rights obligation".

The crackdown and some strongly worded criticism Duterte has made of the United States since coming to power present a dilemma for Washington, which has been seeking to forge unity among allies in Asia in the face of an increasingly assertive China, especially in the strategic South China Sea.

This month, two U.N. human rights experts urged Manila to stop the extra-judicial executions and killings. Duterte responded by threatening to leave the United Nations.

In his speech on Monday Duterte scoffed at accusations that he was trampling on human rights and said law enforcers should not worry about criminal liability while acting on his campaign.

"KILL THEM"

In the early hours of Monday a suspected drug lord and his wife were shot dead by a gunman as they stepped off a ferry in the central province of Iloilo, national police spokesman Dionardo Carlos said.

Police said the man, Melvin Odicta who was also known as "Dragon", was returning from Manila where last week he had met the interior minister to deny accusations that he was the region's top drug dealer.

National Police chief Ronald dela Rosa said on Friday he did not believe Odicta, telling officers: "Who are they fooling?"

In a speech to thousands of drug users and pushers the previous day, dela Rosa encouraged them to kill drug lords because they were getting rich at the expense of the poor.

"You want to kill them, then kill them, you can kill them because you are their victims here. You know who are the drug lords here, go to their houses, pour gasoline, set it on fire, show them you are angry at them."

He later apologised for the comments.