MANILA, August 22(Reuters): Political opponents of Philippine leader Rodrigo Duterte on Tuesday urged him to end a culture of impunity and quell a surge in drug-related killings, amid widespread anger at police over the death of a teenager. Allegations of a cover-up in last week’s death of Kian Loyd delos Santos has caused rare outrage among a public largely supportive of Duterte’s campaign, which saw more than 90 people killed last week in three nights of intensified police operations. The 17-year-old student was killed in a rundown area of Manila and according to a forensic expert who conducted an autopsy, Delos Santos was shot in the back of the head and ears while on the floor, suggesting there was no gunfight, contrary to an official police report. The victim’s family reject police allegations he was a drug courier. Duterte has resolutely defended police on the front lines of his 14-month-old war on drugs, but late on Monday he said three officers involved in the teenager’s killing should be punished if found to have broken the law. Duterte said he had seen the CCTV footage acquired by media which showed plain clothes police dragging a man matching the description of Delos Santos, to a location where he was later found dead. Opposition Senator Leila de Lima, a detained critic of Duterte, challenged the president to order the police to stop killing. “I dare you, Mr President, to issue a clear and categorical order to the entire police force to stop the killings now,” De Lima said in a handwritten note from a detention facility, where she is being held on charges of involvement in drugs trade inside jails, which she denies. ‘STIRRED INTO ACTION’ Another senator, Risa Hontiveros, told the house Duterte had blood on his hands and “reveled in the deaths of drug addicts”, inspiring a culture of impunity and killing. Filipinos tired of crime and drugs and supportive of the president had woken up to what was happening, she said. “You had no choice but to confront his death because his narrative was compelling,” she said of Delos Santos. “You felt stirred into action because you could no longer ignore the growing outrage ... there were thousands of deaths before him and that you allowed it to happen.” Social media users, politicians of all sides and Catholic bishops have called for an impartial investigation into the surge in killings by police, which stopped when news of the teenager’s death surfaced. The Senate will on Thursday hold an inquiry into last week’s bloodshed. Since Duterte took office, more than 3,500 people have been killed in what the Philippine National Police (PNP) says were gunfights with drug suspects who had resisted arrests.