MANILA, Philippines -- Sen. Panfilo Lacson on Thursday tried to test the credibility of a witness at a Senate hearing who claimed to be a member of the Davao Death Squad and who linked President Rodrigo Duterte to killings in Davao City while he was mayor.

Witness Edgar Matobato made the allegations at a Senate committee hearing on alleged extrajudicial killings in the country that have been linked to the government's war on drugs.

Lacson became wary of Matobato's credibility due to inconsistencies in his statements.

Under questioning, Matobato said that he knows Philippine National Police Director General Ronald Dela Rosa, adding he was actually involved in the killing of Sali Makdum, an alleged international terrorist, in 2002.

"Kinuha namin siya sa itaas ng palengke tapos dinala sa opisina ng [Presidential Anti-Organized Crime Task Force, PAOCTF]," Matobato told senators.

"Doon kami sa PAOCTF na sila si Arthur Lascanas, Colonel Tony Rivera, siya talaga ang mga tao niya (Dela Rosa) noon," he also said.

When Lacson asked if Dela Rosa knows Matobato, the PNP chief said he did not.

"Your honor, this is the first time that I see this person," Dela Rosa said. "I [have heard] his name, narinig ko yung pangalan niya, Edgar Matobato sa Davao, tirador daw. Pero yung mukha, di ko kilala. Ngayon ko lang talaga nakita."

Dela Rosa also added that he does not know any Arthur Lascanas, and that the PAOCTF did not have a target named Sali Makdum when he was with the task force.

"I am surprised with this statement, your honor." Dela Rosa said. Lacson said that he could not find any record of a "Sali Makdum" on the internet either.

Lacson said the Senate should test the witness' credibility after Matobato changed his earlier statement that he knew Dela Rosa. Matobato later said he just used to see Dela Rosa at the office.

"Kaya nga gusto ko mag-test tayo ng credibility dito, yung credibility test, kasi kayo yung pangunahing testigo na naririto," Lacson, a former PNP chief, said.

Lacson also said that the PAOCTF, which he used to head, no longer existed in 2002.

Sen. Leila De Lima, chairperson of the Senate Committee on Justice and Human Rights, said that she had received reports that PAOCTF still operated past 2001, when Lacson stepped down as President Joseph Estrada's PNP chief. She said that this can be verified with the Office of the President. -- Kristian Javier