At least nine people were killed Wednesday in a police operation targeting criminal gangs in a complex of slums in Rio de Janeiro, authorities said, the latest in a series of deadly security force raids across Brazil.

Rio state police said officers had returned fire after coming under attack during a raid on a meeting by organized crime leaders in the Complexo da Penha group of favelas, on the city's north side.

The latest deaths come amid mounting calls for independent investigations of alleged police abuses in Brazil, where the security forces have faced accusations of human-rights violations in their war with heavily armed drug gangs.

At least 42 people have been killed in police operations against drug gangs across Brazil in the past six days, including 14 in Sao Paulo state and 19 in the northeastern state of Bahia.

Police in Rio said the latest operation came after officers received intelligence on a high-level meeting by gang leaders.

"A clash occurred when police teams came under attack by gunmen at the scene," they said in a statement.

"Eleven suspects were wounded" and taken to the hospital, it said.

"Nine of them died of their injuries."

A policeman was also wounded and is in stable condition, it added.