Brazilian Army fights drug traffickers in Rio favela
Brazilian security forces have moved into a major Rio de Janeiro slum, after warning drug traffickers to surrender or face an assault.
Exchanges of fire were heard near the Alemao favela, where hundreds of alleged drug traffickers are believed to be hiding.
Some 2,600 police and troops, backed by armoured vehicles and helicopters, are taking part in the operation.
The BBC's Tim Vickery reports from Rio de Janeiro.