No less than 64 civilians died in a police operation targeting the Red Command gang in the Brazilian city's northern districts - the largest and deadliest raid in the area's records.
Four law enforcement personnel were included in the fatalities during Operation Containment in the communities of Alemão and Penha, local authorities said. In excess of 80 people were taken into custody.
Violent conflicts broke out when about 2,500 law enforcement officers initiated the operation on Tuesday morning. The Red Command responded with gunfire, igniting obstacles and dropping bombs from drones, authorities stated.
The International human rights organization stated it felt "horrified" by the police operation, calling for "swift and comprehensive examinations".
The informal settlements adjacent to the aerial transportation hub is regarded as the headquarters of one of Brazil's most powerful criminal organizations.
Government representatives confirmed at least 50 of those killed were "classified by law enforcement as potential lawbreakers".
Many residents were hurt, including non-combatants affected by the violence.
Locals have compared the hillside area - home to about 300,000 residents - to a "battlefield" since the raid started.
Access ways continue shut in the entire neighborhood.
The criminal network has been increasing their control throughout the region, growing illegal substance trade paths and dominance over the slum communities.
Local law enforcement reported in excess of 200kg (441lb) of narcotics were captured in the mission, in addition to numerous weapons.
The coordinated mission by different law enforcement agencies was preceded by a extended probe.
Numerous alleged criminals are believed to be participants in an organization from the Pará state who are currently hiding in Rio de Janeiro.
Large-scale police operations are not uncommon in the country ahead of major international events in the country.
The United Nations climate conference the environmental summit is taking place in the city of Belem in the north in the eleventh month.
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