A top Brazilian police official has been suspended over alleged involvement with paramilitary militias, a police spokesman has confirmed.
Rio's state governor has asked for federal help to curb the violence
The militias have been battling drugs gangs for control of the shanty towns of Rio de Janeiro.
Inspector Felix dos Santos Tostes was suspended from his position as a key adviser to the state's former police chief on 30 January.
Dozens of people have been killed in Rio this month, according to reports.
Clashes over the weekend between the drugs gangs and militia groups left at least seven people dead.
Police spokesman Renato Barone said Tostes was thought to be a leader of a militia formed from renegade police and security forces.
"He was a top adviser to the previous government and when the new police chief took over and learned of Tostes' links to the militias, he was suspended," said the spokesman said.
The militias have taken control of many of Rio's favelas - or shantytowns - from drugs gangs and are charging residents and businesses for protection.
The drugs gangs have been trying to take back their territory, leading to a wave of deadly gunfights this year.
A newly formed watchdog called Rio Body Count, which says it was inspired by the Iraq Body Count group, is trying to keep track of reported violent deaths and injures.
On its website, the group reports that more than 50 people have died in the metropolitan area of Rio de Janeiro since 1 February.
A police spokesman said they would investigate the alleged involvement of security officials in the militias.
Last month, the governor of Rio de Janeiro state requested the deployment of federal security forces to help tackle rising violence.
Rio is gearing up for its world-famous carnival in a couple of weeks and in July the city hosts the Pan American Games.