Philippine President Rodrigo Duterte staunchly defended more than two dozen policemen accused by the government's main investigation agency of killing a jailed mayor linked to illegal drugs.

Duterte said on Wednesday he still believes the accounts of the policemen, who said Mayor Rolando Espinosa Sr and another inmate, Raul Yap, died in their cells when they shot it out with police during a November 5 raid in a jail in central Leyte province.

The president said he was willing to go to jail for his policemen.

Philippine mayor killed in police shoot-out

After weeks of investigation, the National Bureau of Investigation said on Tuesday it determined the two inmates died in a police "rub-out" and not a shoot-out.

The NBI, the equivalent of the United States' FBI, said the policemen probably placed pistols and illegal drugs in the cells of the two dead inmates to justify the police raid.

"What the police stated is the truth for me," Duterte said in a speech. He added he would not allow the policemen to go to jail.

The NBI findings cast a black mark on Duterte's deadly anti-drug crackdown, which has alarmed western governments and human rights groups. There have been suspicions that some of the more than 4,000 slain drug suspects may have been killed deliberately by law enforcers and did not die in gun battles as claimed by police.

NBI spokesman Ferdinand Lavin said on Tuesday that the bureau filed murder complaints against the policemen at the Department of Justice last Friday. Prosecutors will rule whether there is enough evidence to indict the policemen.

All the policemen involved in the raid at the jail conspired to kill Espinosa and Yap and cover up the murders, Lavin said.

Investigators: Philippine police killed jailed mayor

Espinosa's death has sparked scepticism even among politicians backing Duterte's crackdown because of the apparent brazenness of the killings. He had surrendered to the national police chief in a nationally televised event after he and more than 160 other officials were named publicly by Duterte in August as part of a shame campaign.

Espinosa was later released, but was re-arrested and jailed in October after being indicted on drug and firearm charges.

His son, an alleged drug lord, was arrested in the United Arab Emirates in October and has been repatriated to the Philippines, where he has acknowledged past involvement in illegal drugs.

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Source: Agencies