No less than 64 civilians lost their lives in a police operation targeting the organized crime group 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, state officials said. More than 80 people were taken into custody.
Fierce clashes broke out when approximately 2,500 security personnel initiated the operation on the morning of the operation. The Red Command reacted using armed resistance, burning barricades and using drone-dropped explosives, officials said.
The United Nations human rights body said it was "appalled" by the law enforcement raid, demanding "immediate and thorough inquiries".
The area of favelas near Rio's airport is considered to be the central command of a major illegal networks.
Government representatives confirmed a minimum of 50 of the fatalities were "indicated by police as suspected of being criminals".
Dozens of people were wounded, including civilians caught in the crossfire.
Residents have compared the elevated neighborhood - inhabited by approximately 300,000 people - to a "war zone" since the raid started.
Transport routes stay blocked across the area.
The Red Command group have been expanding their control throughout the region, growing illegal substance trade paths and dominance over the slum communities.
Rio's police stated in excess of 200kg (441lb) of drugs were captured in the raid, in addition to multiple guns.
The coordinated mission by civil and military police was preceded by a extended probe.
Many of the individuals are thought to be members of a faction from the northern region who are presently concealed in the city.
Large-scale police operations are not uncommon in Brazil before significant global gatherings in the South American nation.
The UN climate summit COP30 is set to occur in the northern city of Belem in the eleventh month.
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