Sao Paulo officials negligent on human rights - Amnesty
Authorities in Brazil's Sao Paulo state are failing to provide security or justice for victims of human rights violations, Amnesty International says.
It says reports of police involvement in revenge killings have not been investigated properly for "many years".
The claim comes amid a wave of violence in which more than 90 police officers have died this year. In October alone 571 civilians were killed.
A public security spokesman said the state always acted on police abuses.
"The state does not condone criminal police officers," he said, adding that Sao Paulo authorities rigorously enforced the law by arresting and expelling offenders in all sections of the police.
Amnesty's Brazil researcher Tim Cahill told BBC Brasil the state had been negligent in ensuring public security and guaranteeing justice for victims of violence committed by "agents of the state".
Attacks on the police should be condemned, but there was also a need for an independent body with sufficient power to investigate human rights violations, he said.
Since May this year there has been a growing conflict across Brazil's most populous state between the police and a criminal faction known as the PCC, or First Command of the Capital.
Analysts say attempts by the police to deal aggressively with the PCC provoked a violent backlash, with many officers killed, often while off duty.
In response, unidentified gunmen have been carrying out a wave of shootings in poor neighbourhoods, amid claims that rogue policemen have taken the law into their own hands.
A senior police officer has said that the criminal records of some of those killed were checked on police computers shortly before the attacks, but later changed his statement to say this had been a problem "in the past".
Mr Cahill said Amnesty International had followed the issue of violence in Sao Paulo for decades.
"For many years there has been a high number of killings committed by police that are not being investigated," he told BBC Brasil.
"We believe that this has contributed not only to the corruption of the police but to the actual involvement of officers in criminal acts."
In May 2006 the PCC briefly brought the city of Sao Paulo to a halt, killing almost 50 prison and police officers. In the aftermath almost 400 civilians also died.
Police chiefs replaced
Mr Cahill said there was a strong suspicion that the same pattern of events is being repeated now, although he admitted Amnesty did not have "concrete evidence".
"As in 2006, there are indications that the notably high increase in the level of murders in the state of Sao Paulo includes the strong involvement of police officers," he said.
Amnesty says there must be an independent process of investigation and the creation of a national institute of human rights that is independent of the state and has the power to investigate police actions.
The spokesman for Sao Paulo's public security department said while Amnesty International was a respectable organisation, its statement to the BBC was "equivocal".
He said Public Security Secretary Fernando Grella was determined to strengthen and give priority to investigations of recent murders, considering all possible motives in the continuing investigations.
Mr Grella was appointed only four days ago, and has already replaced a number of senior police chiefs.
He has also announced closer working practices between all sections of the police, and more officers on the streets to reassure the public.