MANILA (Updated) -- A retired police officer said Monday that President Rodrigo Duterte, when he was Davao City mayor, ordered and paid him and other members of a so-called liquidation squad to kill criminals and opponents, including a kidnapping suspect, his family and a critical radio commentator.

Human rights lawyers who presented Arthur Lascañas at a news conference said his allegations could be grounds for impeaching Duterte.

But Duterte's camp dismissed Lascañas' statement as a mere “demolition job.”

“The demolition job against President Duterte continues,” Communications Secretary Martin Andanar said in a statement Monday.

“Our people are aware that this character assassination is nothing but vicious politics orchestrated by sectors affected by the reforms initiated by the Duterte administration,” he added.

READ: Palace: Lascañas part of 'demolition job' vs Duterte

Duterte has denied his administration backs unlawful killings of suspects under his deadly crackdown against illegal drugs that is feared to have killed more than 7,000 mostly drug users and petty drug pushers since he took office in June.

The killings under the crackdown, an expansion of his anti-drug campaign when he was a longtime mayor of Davao City, have alarmed the United States, other Western governments and the UN rights officials.

In many public speeches, Duterte has told policemen to defend themselves if drug suspects fight back and has openly threatened drug lords and dealers with death.

Lascañas's comments came after he denied to a Senate hearing last year that he had been involved in any extra-judicial killings in Davao. He testified at the inquiry last October 2016 after he was implicated by another witness, Edgar Matobato, a former militiaman who said Duterte ordered him and others to kill criminals in gangland-style assaults that left hundreds of people dead.

Breaking into tears at one point, Lascañas said Monday, February 20, that he was speaking up because he was bothered by his conscience, including his role in the deaths of his two brothers, whom he ordered killed because they were drug users.

"I had my own two brothers killed. Even if I end up dead, I'm content because I've fulfilled my promise to the lord to make a public confession," he said.

Lascañas narrated several killings that he said Duterte had ordered, permitted or financed as mayor of Davao, including the 1993 bombing of mosques as retaliation after Muslim rebels were blamed for the bombing a Roman Catholic cathedral.

Lascañas said he and his group shot dead a kidnapping suspect along with the man's pregnant wife, young son, father-in-law and two others with the consent of Duterte.

After his group informed Duterte about the capture of the suspected mastermind of a kidnapping in Davao, Lascañas quoted the mayor as saying: "All right, make it clean."

Another target was radio commentator Jun Pala, who was critical of Duterte. He was killed in 2003 by gunmen, who then got financial rewards from the then mayor, Lascañas said.

He said the members of the supposed death squad were paid by Duterte, from P20,000 up to P100,000 depending on their target.

"Mayor Duterte was paying us P20,000 sometimes, or P50,000, and it depends on the status of our target. Sometimes, it’s P100,000. I am receiving the allowance from the Office of the Mayor [at the rate of] P100,000," he said. "The existence of Davao Death Squad or DDS is real."

Lascañas was presented by Senator Antonio Trillanes IV at the Senate early Monday, February 20. (AP/With Ruth Abbey Gita/SunStar Philippines)