Residents watch as Brazilian Navy soldiers in an armoured vehicle patrol the Mare slums complex in Rio de Janeiro, April 5, 2014. The federal troops have taken control of security operations in Mare slums complex to help quell a surge in violent crime following attacks by drug traffickers on police posts in three slums on the north side of the city, government officials said. Less than three months before Rio welcomes tens of thousands of foreign soccer fans for the World Cup, the attacks cast new doubts on government efforts to expel gangs from slums using a strong police presence. The city will host the Olympics in 2016. (Photo by Ricardo Moraes/Reuters)

A police officer takes up position during an operation at the Mare slums complex in Rio de Janeiro March 25, 2014. (Photo by Ricardo Moraes/Reuters)

A policeman of Special Operations Battalion (BOPE) looks for drugs and weapons at the Mare slums complex in Rio de Janeiro March 30, 2014. (Photo by Ricardo Moraes/Reuters)

Policemen take position during an operation in the Mare slums complex in Rio de Janeiro March 26, 2014. (Photo by Ricardo Moraes/Reuters)

A Brazilian Army soldier walks past bullet holes in a wall during an operation in the Mare slums complex in Rio de Janeiro March 26, 2014. (Photo by Ricardo Moraes/Reuters)

Boys play soccer as a policeman patrols one day after the occupation of the Mare slums complex in Rio de Janeiro, March 31, 2014. (Photo by Ricardo Moraes/Reuters)

A police officer takes up position during an operation at the Mare slums complex in Rio de Janeiro March 25, 2014. (Photo by Ricardo Moraes/Reuters)

Residents observe a police officer take up position during an operation at the Mare slums complex in Rio de Janeiro March 25, 2014. (Photo by Ricardo Moraes/Reuters)

Police helicopters fly over the Mare slums complex in Rio de Janeiro March 30, 2014.The federal troops and police occupied the Mare slums complex on Sunday to help quell a surge in violent crime following attacks by drug traffickers on police posts in three slums on the north side of the city, government officials said. (Photo by Ricardo Moraes/Reuters)

A navy soldier patrols on a soccer field during an operation to occupy the Mare slum complex in Rio de Janeiro, Brazil, April 5, 2014. More than 2,000 Brazilian Army soldiers moved into the Mare slum complex April 5, 2014 in a bid to improve security and drive out the heavily armed drug gangs that have ruled the sprawling slum for decades. (Photo by Felipe Dana/AP Photo)