Security is still tight in a Rio shanty town hit by fighting between rival drugs gangs at the weekend that left at least 10 dead.
Some 1,200 armed police are on patrol in the Rocinha slum
Rio de Janeiro authorities had asked for 4,000 troops to be sent in to help quell violence in the city's slums.
But the federal government turned the request down, arguing the situation was now under control.
Drug-related killings in Brazil's shanty towns have given the country one of the world's highest murder rates.
Police officers armed with machine guns and wearing bullet-proof vests stood on almost every corner in the vast shanty town of Rocinha on Wednesday, Reuters reported.
Black armoured police trucks and patrol cars formed checkpoints on the streets.
Rocinha - home to 150,000 people - was hit by a wave of shootings over the weekend, as gangs fought for control of some of the most lucrative cocaine distribution points.
Several bystanders were reported to be among the 10 people killed.
Rio officials wanted the government to send in federal soldiers to help keep the peace.
But Justice Minister Marcio Thomaz Bastos rejected their request at a meeting in Brasilia with Rio's Public Security Secretary Anthony Garotinho.
"The federal government's intelligence services have concluded there is no need to send the army in," Mr Garotinho said afterwards.
Mr Garotinho is to pursue the request with the defence ministry, according to Reuters.
Meanwhile, Brazilian media reports that a man shot dead in Rocinha on Wednesday is believed to the leader of one of the gangs.
Luciano Barbosa da Silva, known as Lulu, was killed in a gunfight with officers, reports said.
Troops were deployed in Rio in February 2003 during Carnival celebrations, following a similar wave of violence.
Unlike most shantytowns or "favelas", Rocinha is in a luxury beachside zone of the city - a tourist magnet - and some analysts suggested the violence might have come too close for comfort for Rio's wealthiest inhabitants.
"Drug gangs are almost always fighting for territory," Rubem Cesar Fernandes, president of the human rights group Viva Rio, told AP.
"The difference is that this time it happened in slums which are part of the 'beautiful' side of Rio."