Police in Brazil's two biggest cities routinely execute suspects and cover up the killings as self-defense. That's the claim of U.S. based group Human Rights Watch, which released a report about officers in Sao Paulo and Rio de Janeiro.

In a two-year investigation, the rights group said it found evidence that many victims had not resisted arrest, as claimed by the police.

Daniel Wilkinson, Human Right Watch's Deputy Director for the Americas, said police officers are rarely punished for the deaths of suspects.

[Daniel Wilkinson, Deputy Director, Human Right Watch]:
"The impunity following extrajudicial executions committed by police agents unfortunately continues to be abnormal as a general
rule."

The report said that many of the slain were found to have been shot at close range and that police allegedly cover up their killings by destroying crime scene evidence.

Isabel Jennerjahn, a member of a Rio network of groups against violence, said that witnesses to the killings were often scared off by police threats.

[Isabel Jennerjahn, Rio de Janeiro's Groups Against Violence]:
"The state that talks to us about human rights is the same state that gives awards to police officers who execute people. This is an
obstacle for our work."

Police in the states of Rio and Sao Paulo have killed more than 11,000 people since 2003, making them among the most lethal in the world.

Rio's state government is under pressure to reduce violence levels ahead of the 2014 World Cup and 2016 Olympic Games.