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 Brazil's history.

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

As approximately 2,500 security personnel moved in on Tuesday morning, fierce clashes erupted. The Red Command (Comando Vermelho) responded with gunfire, setting up burning barricades and using drones to drop explosives, officials reported.

The UN Human Rights Office expressed horror at the police operation and called for prompt and effective investigations.

This area of favelas, near Rio's airport, is considered the headquarters of one of Brazil's most powerful organized crime groups.

Authorities indicated that at least 50 of those killed were suspected criminals, highlighting the complicity of gang activity in the violence.

The clashes resulted in injuries to dozens of individuals, 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 began, with roads remaining closed in the region as tension persists.

The Red Command gang has been expanding its territory across Rio state, increasing drug trafficking routes and control over the hilly favelas.

Authorities reported the seizure of over 200kg of drugs and numerous firearms during the raid, conducted as part of a year-long investigation.

Dozens of the suspects are thought to be members of a faction from Pará state, currently hiding in Rio de Janeiro. Such large-scale police operations are common in Brazil ahead of significant international events, like COP30 scheduled in November in the northern city of Belem.