Military armoured vehicles were sent into a Rio de Janeiro slum as Brazil's security forces sought to restore order after five days of violence that killed at least 26 people.

Military armored vehicles carried police into the heart of a gang stronghold, chasing gunmen into nearby shantytowns and setting the stage for what many people expect to be a bloody battle in Rio's offensive to quell a surge of criminal violence.

Authorities didn't say if police would immediately push into those slums, but said federal police would join the operation Friday to help hold territory taken from the gangs. Holiday leave and all administration duties have been cancelled for police since Tuesday, as the authorities flooded the streets with thousands of extra officers targeting about 28 shanty towns, known as favelas.

Heavily armed gang members have attacked police stations and stopped cars and buses, robbing passengers of money and valuables before setting vehicles alight.

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The scenes of carnage that have spread across large sections of the city since Sunday threaten seriously to undermine Rio's standing as a suitable host for the 2014 World Cup and the 2016 Olympics.

Most of the dead were killed in gun battles with police in which two officers were wounded. One victim was reported to be a 14-year-old girl hit by a stray bullet.

The authorities in Rio believe the violence was ordered by imprisoned gang leaders in retaliation for attempts by police to reassert control over Rio's favelas before sporting events.

''This is a desperate attempt to weaken our security efforts,'' said Sergio Cabral, Governor of the state of Rio de Janeiro. ''What they want is to create panic, for society to retreat, but we will not retreat.''

Police said on Thursday that they were concentrating their efforts on the Vila Cruzeiro favela, where they say drug dealers are hiding after they were forced out of other slums.

Six M113 armoured vehicles from Brazil's Marine Corps were deployed, supported by armed police.

By yesterday troops had taken control of Vila Cruzeiro and police would hunt down the criminals who fled, said Mario Sergio Duarte, general commander of Rio de Janeiro state's military police.

''Territory has been taken away from them,'' said Jose Beltrame, Rio de Janeiro State Security Secretary. ''It's important to arrest these people but it's even more important to take over their territory.''

At least 47 people have been arrested since the start of the violence, some of them caught holding bottles filled with petrol, while weapons and drugs have also been confiscated.

About a third of Rio's 6 million people live in more than 1000 slums, many of them located close to some of the wealthiest areas of the city such as Ipanema, Leblon and Copacabana.

The Brazilian President, Luiz Inacio Lula da Silva, pledged support for the Rio de Janeiro State Governor's drive to fight organised crime.

''Whatever help he needs from the federal government to allow good people to live in peace, we will do it,'' Mr Lula da Silva said.

The President-elect, Dilma Rousseff, pledged to continue Mr Lula da Silva's support in a telephone call with Mr Cabral.

Mr Beltrame said on Wednesday that the city's two main rival criminal organisations, based in the Rocinha and Morro do Alemao favelas, might unite to react to growing police efforts to take over shanty towns.