MANILA - Philippine National Police (PNP) chief Director General Ricardo Marquez on Friday expressed doubts on the vow of Davao City Mayor Rodrigo Duterte to wipe out criminality within six months if he wins as president.

Marquez pointed out that even the most advanced countries have failed to completely eradicate criminality.

"Baka salita lang yun kasi even the most advanced countries with the best police equipment, they have CCTV [cameras] around them, but you know, drugs continue to happen even in the most advanced countries in the world. Crime will be a part of our lives," he said.

Duterte, who is running on a platform of transforming the country into a crime-free showcase, has been quoted as saying that he will order the police and the military to kill outlaws.

He added that he will claim responsibility for the order if complaints are filed against law enforcers.

READ: Kill the criminals! Duterte's vote-winning vow in Philippines

But Marquez stressed that law enforcers should never allow themselves to be "executioners" and directly disobey their mandate to "serve and protect."

"It is important sa kapulisan na naintindihan nila yung trabaho nila: do policing within the bounds of the law," he said.

"Hindi pwedeng ang pulis ang magiging executioner. Hindi pwede 'yung labag at sala doon sa core cause ng pagpupulis which is to serve and protect."

The PNP chief also asserted that policing is a "deliberate science," and there are other ways to combat crime.

As an example, he pointed out that PNP's Oplan Lambat Sibat succeeded in reducing crime incidents in Metro from 918 per week to 300.

Marquez added that genuine peace cannot be achieved through "shortcuts."

"Hindi kami naniniwala doon sa shortcut methods of policing kasi wala namang karapatan ang pulis, it is not within our powers to execute anybody. It's not our job," he said.

"Our job is to investigate crimes, prevent crimes, arrest those responsible for the crimes." -- Report from Jon Ibañez, dzMM