The relentless anti-drug campaign of President Rodrigo Duterte has been featured again by US-based publication The New York Times -- this time, in a 15-minute documentary that delves into the victims of summary killings, their grieving relatives, and the journalists who cover them.

"We sent a film crew to the Philippines, where death, grief and fear fill the streets," the publication said in a trailer for the documentary "When a President Says, 'I'll Kill You,'" which was released Sunday.

Among those featured in the investigative piece is veteran photojournalist Raffy Lerma, who has covered nightly killings of drug killings in Metro Manila.

"The President promised this, he promised that people will die. I am for the drug war, I want drugs to stop, but I'm not for the killing," Lerma told the New York Times.

"There's injustice going on around the country. And you begin to feel maybe we're just starting."

Also featured in the documentary is a professed hitman allegedly hired to murder drug suspects.

"Ang mga pinapatay rin namin talagang mga totally na masasamang tao. Wala na po kaming takot o konsensya para sila ay patayin," the self-tagged assassin said.

President Duterte on Saturday justified the deaths of thousands of poor drug peddlers in his war on crime, saying: "You say that they are only killing the poor people. Well, I am sorry, I have to clean up, and until such time that the drug lords are dead, are out of the streets, walking at night, you'll all be consumed."

Duterte however reiterated that only those who resisted arrest were killed in police efforts against drugs.

Watch the full New York Times documentary on the war on drugs below:

The New York Times also published last week an editorial urging the international community to suspend Manila's trade incentives in order to hold Duterte accountable for the spate of drug-related killings.

• NY Times wants accountability for Duterte: 'Hit PH where it hurts most'

The paper previously published an editorial cartoon on Duterte's campaign in August and a special drug war report titled "They Are Slaughtering Us Like Animals" last December.