Brazilian reconnaissance troops entered a sprawling slum district near Rio's international airport on early Wednesday ahead of a larger operation to secure the crime-ridden area ahead of the World Cup.

The federal troops joined police in the deployment in Mare to set the stage for a major joint drive to "pacify" a cluster of 16 neighborhoods seen as havens for organized crime.

Rio authorities last week asked the government to approve military support for police in favelas in thrall to violent gangs and drug traffickers after a series of attacks on police units.

Authorities are stepping up efforts to quell the violence as the World Cup looms ever closer.