A minimum of 64 individuals were killed in a law enforcement action cracking down on the criminal organization Comando Vermelho in the Brazilian city's northern suburbs - the largest and deadliest raid in the Brazilian state's history.
Four law enforcement personnel lost their lives during the police action in the Alemão and Penha districts, state officials stated. In excess of 80 suspects were arrested.
Violent conflicts broke out when approximately 2,500 security personnel moved in on Tuesday morning. The criminal organization countered with shooting, setting fire to barriers and dropping bombs from drones, officials said.
The United Nations human rights body said it was "horrified" by the security action, urging "swift and comprehensive examinations".
The informal settlements close to Rio's airport is considered to be the main base of one of Brazil's most powerful illegal networks.
Local authorities stated no less than 50 of the deceased were "identified by authorities as alleged offenders".
Dozens of people were injured, including innocent bystanders trapped in shooting.
Locals have likened the hillside area - inhabited by approximately 300,000 people - to a "battlefield" since the operation began.
Access ways continue shut across the area.
The Red Command group has been increasing their territory across the Rio state, growing illegal substance trade paths and power in the informal settlements.
Local law enforcement said more than 200kg (441lb) of narcotics were seized in the operation, along with dozens of firearms.
The coordinated mission by civil and military police was preceded by a extended probe.
Many of the individuals are thought to be affiliates of a group from the northern region who are presently concealed in Rio de Janeiro.
Extensive security missions are regular in the country prior to significant global gatherings in the South American nation.
The UN climate summit the environmental summit is taking place in the northern urban center in late autumn.
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Debra Briggs
Debra Briggs