Amnesty International warned Thursday that police violence against peaceful demonstrators could damage the World Cup, and called on Brazil to respect the right to protest.
Brazil has been hit by a wave of protests against the more than $11 billion being spent on the World Cup, which kicks off in one week.
The rights group said the police response had been characterized by violence and abuses including arbitrary arrests and the indiscriminate firing of tear gas and rubber bullets against peaceful protesters.
"Brazil's deficient policing record, reliance on the military to police demonstrations, lack of training and an atmosphere of impunity creates a dangerous cocktail in which the only losers are peaceful protesters," Atila Roque, Amnesty's country director for Brazil, said in a statement.
Amnesty said hundreds of protesters had been wounded by police in crack downs on the protests that erupted a year ago as Brazil staged the Confederations Cup, a World Cup dress rehearsal.
It cited the case of a photographer who lost an eye after being struck by a rubber bullet.
The rights group said it had presented a petition with 90,000 signatures to Brazilian President Dilma Rousseff's office calling for protesters' rights to be protected.