Heavily armed troops and police units surrounded Rio's slums known as favelas before dawn on Saturday.

Rio's state security service said 3,600 soldiers and 1,300 police were deployed to stop gangs behind a surge in brazen robberies on commercial trucks.

Read more: Rio's Olympic legacy

By mid-afternoon, "two criminals were killed in confrontations," said security chief Robert Sa.

Residents said they were subjected to identity checks and body searches and had been awoken by the sound of shooting.

"They treat us as if we're trash," said one resident named Roberto, quoted by the news agency AFP.

Defense Minister Raul Jungman told Globo TV that troops would remain in Rio as long as necessary.

Saturday's troop deployments were part of 8,500 sent to Rio last month in a tacit acknowledgement that cash-strapped police had lost the ability to cope.

Road blocks

The five favelas surrounded were Lins, Camarista Meier, Morros de Sao Joao, Engenho Novo in Rio's north, and Covanca in the west of the metropole.

Authorities said roads had been blocked and airspace restricted to civilian flights over the areas raided. Rio's airports, however, were not affected.

Saturday's crackdown came exactly one year after President Michael Temer opened the Olympics, the first held by any South American city. The facilities offer great potential for the city in what could make Rio one of Brazil's most prosperous regions.

Crime, corruption, deprivation

Instead there have been surges in crime and corruption linked to Brazil's hosting of the 2014 football World Cup and the 2016 Rio Olympics. State coffers have been bled dry. 

In June, former Rio governor Sergio Cabral was jailed over corruption involving infrastructure contracts for the Games.

In the first six months of 2017, Rio experienced a 14-percent rise in murders to 3,755. The number of persons killed by police soared to 581.

Last Monday, a funeral for an unborn baby killed by a stray bullet during a shootout between police and a drug gang, was held in a northern Rio slum.

Public safety had deteriorated "dramatically," said Amnesty International.

"We see clearly that the Olympic promise of a safe city has not been fulfilled," said Amnesty research coordinator Renata Neder.

Last Sunday, hundreds of slum residents converged on the posh Copacabana beach to plead for an end to lethal shootouts.

Funds dried up

Gains made by policing in the several years before the games, such as evictions of drug gangs, had withered away, partly because post-Olympics funds had dried up.

Critics accused authorities of failing to make good on promised social advances for the slums. Residents had pleaded for better sewage and sanitation systems, which often did not materialize.

Deploying the army would not solve problems such as gang battles for territory, said security expert Ignacio Cano of Rio's state university.

"Under the best scenarios, the armed forces will leave, and everything will continue normally," Cano said.

ipj/bw (AFP, Reuters, AP)