Four suspected drug traffickers died in a police operation Tuesday in a "favela," or shantytown, in Rio de Janeiro, Brazilian police said.

Eight police units took part in the operation in Morro da Pedreira, a shantytown on the outskirts of the city.

Officers seized a rifle, three pistols and 450 doses of crack cocaine, police said.

The operation was staged to try to capture a suspect wanted for the killing of a police officer on Monday night in Morro da Pedreira.

Officer Marcos Vinicius Saldanha was kidnapped and shot dead by unidentified individuals when he stopped to fill up his automobile at a gas station in the favela, media reports said.

Rio de Janeiro has become one of the most dangerous cities in Brazil due to the constant clashes involving drug gangs, police and death squads.

A third of Rio's 6 million people live in dwellings in the favelas, where drug traffickers often wield power through violence, replacing the government.

In some 200 shantytowns, according to official estimates, drug traffickers have been pushed out by death squads made up of active-duty and retired police officers, who take justice into their own hands, creating a new challenge for the government.

The Rio de Janeiro state government plans to construct permanent police substations in all favelas before the 2016 Olympic Games.