Brazilian President Luiz Inacio Lula da Silva said on Tuesday that the police operation against a powerful criminal faction in Rio that left 121 dead was "a massacre."

"There was a massacre, and I think it's important to verify the conditions under which it occurred," Lula said in the Amazon city of Belem during an interview with international news agencies.

The police raid last week against the Red Command drug trafficking gang saw thousands of officers battle heavily armed men dressed in camouflage, who dropped explosives on police from drones.

Police footage released by local media shows members of the gang gearing up for the fight, with dozens streaming into a forested area where they clashed with elite security forces, and where many of the bodies were found the next day.

The battle exposed Rio de Janeiro's chronic security woes and divisions on how to tackle them.

While rights activists have denounced harrowing scenes of dead bodies lined up in the street, surveys showed many of the city's crime-weary citizens supported the operation.

Felipe Curi, the head of Rio's Civil Police force told reporters on Friday that police had so far identified the bodies of 99 "criminals" among the dead – 42 of them subject to arrest warrants and 78 with extensive criminal records.

Amid criticism that his administration is too lenient on crime, Lula said on X on Friday that he had submitted a bill to parliament proposing a minimum 30-year prison sentence for gang members. (AFP)