Philippine police are under pressure to explain the killing of a 17-year-old high school student, who has become the latest victim of President Rodrigo Duterte's ruthless war on drugs.

Kian Loyd Delos Santos died on Thursday night in the capital Manila amid allegations that he was framed by three police officers, who witnesses said forced the teenager to hold a gun, fire and run.

CCTV footage from the Manila suburb of Caloocan showed Delos Santos being carried by two men to a place where his body was later found, raising doubt about an official report that said he was shot because he fired at police officers first.

According to the police report, Delos Santos ran when he saw the officers approaching him. He then pulled out a gun and opened fire at the policemen, who shot back.

Witnesses told local media that the teenager was unarmed.

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National police chief Ronald dela Rosa said that if the Grade 11 student did not pose a threat, the officers who shot him on Thursday night would be held accountable.

"I will not allow any police officer to just kill a 17-year-old boy for no reason at all," he told reporters. "Are they that heartless?"

Dela Rosa added: "Just think about it, he is just a kid. If that happened to your sibling? We will investigate it, I assure you."

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Metro Manila police chief Oscar Albayalde said the three policemen involved had been relieved of their duties and an investigation would be launched.

Kian Lloyd delos Santos is an 11th grader. Police handed him a gun to shoot, then shot him for it while he cried. He wanted to be a cop. pic.twitter.com/r6LXC8nqcs — dani 🥐 (@quaxon) August 18, 2017

Several senators, including known allies of Duterte, expressed outrage about Delos Santos' death and called an investigation on Friday into a spike in the killings of drug suspects in recent police operations.

"The Philippine National Police, on its misguided war on drugs, is now terrorising our communities and collateral damage is unacceptable," said Representative Edgar Erice.

"Killing the poor and powerless is not the solution to the drug problem when tons of methamphetamine are smuggled in," Senator Francis Pangilinan said in a statement.

'Bloody week'

Police killed at least 27 people in Manila on the third night of a new push in Duterte's war on drugs and crime, taking the toll for one of the bloodiest weeks so far to 94, according to officials.

Earlier in the week, 67 people were shot and nearly 250 arrested in Manila and provinces adjoining the Philippines capital, in what police described as a "One-Time, Big-Time" push to curb drugs and street crime.

President Duterte hailed the recent killing of 32 drug suspects in a 24-hour police crackdown, the highest death toll in a single day in his administration's anti-drug war.

"That's beautiful. If we can only kill 32 every day, then maybe we can reduce what ails this country," Duterte said on Wednesday.

According to police statistics, more than 3,000 suspects have been killed in anti-drug operations since Duterte became president on June 30, 2016.