Brazilian security forces launched a raid against a slum where between 500 and 600 drug dealers are based.
Police forces, supported by tanks and helicopters, moved into the Rio de Janeiro neighbourhood amid a heavy exchange of fire early this morning local time.
About 2,600 soldiers and members of elite police units took part in the operation targeting a lawless group of slums dubbed Complexo de Alemao.
Police seized weapons and large quantities of drugs as they swept through the deserted streets of Alemao in search of traffickers.
Among the traffickers being hunted in Alemao were some who had fled from the Vila Cruzeiro slum after police invaded last week and have occupied it since.
At least 46 people, most of them suspected traffickers, were killed in gun battles to take control there.
Police regularly invade Rio's crime-infested favelas in search of traffickers but the large number of troops involved in these operations and their occupation of the zones was unusual.
Military police spokesman Colonel Lima Castro said: 'This is our D-Day. We will return this community to the people of Rio de Janeiro.'
Military Police Commander General Mario Duarte told reporters that authorities had the criminals 'outgunned'. There was 'no possibility the drug traffickers can succeed', he added.
Gen Duarte said: 'We will not be losing any ground in our move to bring peace to Rio. We are getting close to the end of getting the traffickers in Alemao.'
Defence Minister Nelson Jobim authorised the deployment of ten military armoured vehicles, two Air Force helicopters and 800 soldiers to reinforce the police already engaged in the operation.
There is a sense of urgency in a Brazil that has emerged as a global economic and political player and soon will host the world at home.
Authorities are seeking to impose order on the violent slums before Brazil hosts the World Cup in 2014 and the Olympic Games two years later.
