At least 64 people were killed in a police operation against the Red Command gang in Rio de Janeiro's northern suburbs - the largest and deadliest raid in the Brazilian state's history.

Four police officers were among those killed during Operation Containment in the Alemão and Penha districts, state Governor Cláudio Castro said. More than 80 people were arrested.

Fierce clashes erupted when approximately 2,500 security personnel moved in on Tuesday morning. The Red Command (Comando Vermelho) responded with gunfire, burning barricades, and dropping bombs from drones, officials noted.

The UN Human Rights Office expressed being horrified at the police operation, urging for prompt and effective investigations.

The area of favelas near Rio's airport is deemed the headquarters of one of Brazil's most powerful organized crime groups. State officials indicated that at least 50 of those killed were suspected criminals.

Dozens were injured, including civilians caught in the crossfire. Locals have described the hillside area - home to around 300,000 residents - as resembling a war zone since the operation commenced.

Roads remain closed throughout the region, and the Red Command has been expanding its territory across Rio state, enhancing its drug trafficking routes and control over the hillside favelas.

In the raid, the police seized over 200kg (441lb) of drugs and numerous firearms. This intense operation followed a year-long investigation.

Police suggest that many of the suspects are members of a faction from Pará state currently hiding in Rio de Janeiro. Such large-scale police operations are common in Brazil ahead of major international events, including the upcoming UN climate summit COP30 in the northern city of Belem in November.