New York-based Human Rights Watch said its investigation showed 814 suspected drug dealers, petty criminals and street children allegedly involved in gangs were gunned down as a crime deterrent between 1998 and February 2009 in Davao city. Thirty-three killings were reported in the southern city in January alone.
The report included the case of four brothers aged 14-18 killed one after the other from 2001 to 2007. The youngest, 14, was fatally stabbed in 2003 in a market just two days after his mother secured his release from police who arrested him for allegedly stealing a cell phone.
"The hundreds of targeted killings in Davao city in recent years are clearly not random events but the result of planned hits by a 'death squad' that involves police officers and local officials," said Kenneth Roth, executive director of Human Rights Watch.
"The police consistently fail to bring the perpetrators to justice, while the local government cheers from the sidelines," said Roth.
The group urged President Gloria Macapagal Arroyo to investigate the killings and hold the perpetrators accountable.
National police chief Jesus Verzosa said he has ordered an intensified investigation but denied the killings were state-sponsored.
Davao Mayor Rodrigo Duterte - who has cultivated an image of a crime-buster and goes around carrying a gun - blamed the killings on gang wars and drug addicts but refused to directly answer questions on the death squads Tuesday.
"I would still utter the same statements: that we are here to protect the law-abiding and God-fearing citizens and to make it doubly hard for criminals to do their thing here," he told reporters.
However police statistics show that crime in Davao has actually increased 219 percent over the last decade.
Roth said evidence so far showed low-level police involvement and did not directly link Duterte or senior police officials to the killings. But he said the mayor has given active blessing to murder as a solution to criminality, giving tacit signal to death squads to continue their work.
The group said it investigated 28 killings and obtained information from relatives and friends of death squad members, journalists, community activists and government officials.
Most death squad members were former communist New People's Army insurgents who surrendered to the government or young men who were targeted and joined the group to avoid being killed, it said.
Police officers or ex-police officers provided the death squads with training, weapons and ammunition, motorcycles, and information on the targets, Human Rights Watch said.
Police were deliberately slow to respond to killings enabling death squad members - who operate in twos or threes on a motorcycle without a license plate - to escape the crime scene.