A 28-year-old vendor who survived a police operation that killed four drug suspects in the Philippines today asked the Supreme Court to stop the government's campaign against illegal drugs.

The petition was the first case filed to challenge President Rodrigo Duterte's aggressive drug war, which has killed thousands since July.

Lawyer Romel Bagares said his clients - Efren Morillo and family members of the four slain suspects in the August operation - also asked the Supreme Court to order the police to stop threatening witnesses.

"Morillo continues to fear for his life," according to the petition.

"Because he survived the attack of the perpetrators and identified each and every one of them, his life is in grave danger."

According to the petition, four policemen barged into one of the houses of the victims in the slum village of Payatas in metropolitan Manila in August and shot the suspects.

Three of the men were made to "kneel on the ground at the back of the house" and then they were shot dead, the petition said.

One of those slain "begged to be spared, hugging the legs of one of the armed men and sobbing," it added. "As he would not let go of his hold, the man shot him (in) the nape."

Police claimed the men were drug dealers and fought back during the operation, but Morillo denied the accusation and noted that they were rubbish collectors and scavengers.

Bagares said the petition is currently only asking the Supreme Court to stop the implementation of the campaign against illegal drugs in Payatas, but he hoped that it would encourage other victims to file similar cases.

"We hope that the other victims will be emboldened to seek the help of the courts," he told reporters. "We understand the need to fight the drug menace in society but we are a civilized nation, we have laws, and we want that law to be followed."

Since July 1, 2,517 suspects had died in police operations against drug users and pushers by Jan 25, according to police statistics.

Police are also investigating nearly 3,000 additional deaths in the first six months of Duterte's presidency, including possible vigilante killings in connection with the drug war.

Most of the victims of these "deaths under investigation" were found dead in streets and back alleys in the country, many bound in tape and with a sign saying, "I'm a drug pusher. Do not be like me."

- dpa