Brazilian police have killed more than 11,000 people over the past five years, averaging about six killings a day, a group that monitors violence says.
The Brazilian Forum on Public Safety said law enforcement agents in the US, by comparison, had killed a similar number over the past 30 years.
The report by the Sao Paulo-based body accused Brazilian police of making "abusive use of lethal force".
The study said Rio de Janeiro state had the highest per capita rate of killing.
Some 416 people were killed in the state in 2013, according to the report quoted by the Associated Press news agency.
The study also said 50,806 people had been killed in homicides in Brazil last year - an average of about one person every 10 minutes.
The vast majority of the victims were black and more than half were in their late teens or twenties, the report said.