Dozens of people have been killed in Rio de Janeiro, Brazil's second largest city, in a massive week-long crackdown on drug gangs.

Brazilian police backed by federal troops are battling drug gangs that control Rio's shantytowns - also known as "favelas". Moving from one favela to the next, this major crackdown began almost a week ago now.

Authorities say the violence started when jailed gang leaders ordered their followers to attack police stations.

But it could also be a part of major clean-up operation as Brazil prepares to host the 2014 Fifa World Cup and the 2016 Olympics.

Can the government win this battle and how powerful are these gangs?

This episode of Inside Story aired from Saturday, November 27, 2010.

Source: Al Jazeera