tells CNN, take them to a quiet part of town -- like a quarry -- and kill them before dismembering the bodies, dousing them in oil to keep them from smelling as they decomposed and burying them, or dumping them at sea, Matobato says.

For those disposed of at sea, they'd hack open their victims' chest cavities, to ensure that the corpses sank, he recalls.

He says that the orders mostly came from a ranking police officer, but on occasion, he says, Duterte himself would order the killings.

In 1993, after the bombing of the city's cathedral, Matobato says, Duterte personally told him and other DDS members, in the mayoral office, to go to a mosque and kill Muslims in reprisal for the terror attack.

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On a different occasion, he alleges Duterte shot and killed a National Bureau of Investigation agent after a traffic altercation led to a shootout. The then-mayor emptied two full magazines of bullets into the agent, he said.

Parallels with war on drugs

In the six months since Duterte took office as president, lurid images of extrajudicial killings crop up every morning in Filipino newspapers -- vigilante justice, or police operations known as "buy busts" that invariably end in the death of the alleged dealer.

Matobato says they bear the hallmarks of those perpetrated by the DDS -- faces bound in electrical tape, crude cardboard signs around the victims' necks, proclaiming their alleged crimes.

Photos: Philippines drug crackdown Police patrol a shanty