Amnesty International said the Brazilian government's inability to provide security has turned the country's largest cities into a "patchwork of violent fiefdoms" controlled by drug gangs and paramilitary militias.
The rights group, in a report scheduled for release today, said government negligence has left poor Brazilians in the crossfire between police and criminals - the victims of stray bullets, police curfews and extortion by militias and drug traffickers.
"Rio de Janeiro and São Paulo have reached a tragic impasse," said the report, based largely on news reports and academic studies. "Criminal gangs . . . have rushed to fill the vacuum left by the state, Balkanizing the cities into a patchwork of violent fiefdoms."
Amnesty said the situation came to a head in São Paulo a year ago when the First Capital Command gang brought South America's largest city to a standstill, torching buses, attacking police stations and taking hostages. Police responded by killing hundreds of suspects.
More recently, drug gangs in Rio launched a wave of attacks that left 19 people dead in response to the growing power of paramilitary militias made up of former and active-duty police, firefighters and soldiers.
Amnesty has called on federal and state governments to "develop a coherent long-term security policy that focuses on the root causes of violence and social exclusion".
Responding to the report, Rio state Governor Sergio Cabral told reporters that police are making welcomed advances in areas dominated by drug gangs.