|Riot policemen are expected to clash with the masked, armed gang members setting up positions in Vila Cruzeiro [AFP]
Military armoured vehicles have rolled into the Vila Cruzeiro slum in northern Rio de Janeiro in support of a police crackdown on Brazilian drug gangs.
Thursday's show of strength came after five days of unrest in the city, during which police stations were attacked and armed groups stopped vehicles, robbed the occupants and set fire to cars.
At least 23 people have been killed and 153 have been arrested as Brazilian security forces seek to crush the gangs and impose the law in the violent slums, known as favelas.
The crackdown has seen police deploying armoured personnel carriers, helicopters and thousands of heavily armed agents.
It is part of the government's wide-spread strategy to control crime in the favelas in the lead up to the country's hosting of the World Cup in 2014 and the Olympic Games in 2016.
Footage from Brazil's TV Globo showed heavily armed drug traffickers escaping to a neighbouring community on pick-up trucks and motorbikes, running through dirt roads on the top of hills.
But Lilia Teles, a TV Globo reporter, told Al Jazeera that that criminals are still setting fires to buses and cars in the city, and that shotgun blasts can be heard in Rio's streets.
Bloody clash anticipated
Al Jazeera's Gabriel Elizondo has been monitoring the situation from Sao Paulo, and said that the public hospital nearest to Vila Cruzeiro has been "urgently sending out messages for all of the trauma doctors to please come to the hospital immediately, because they're expecting that this could get very bloody".
He also reported that while police in Rio de Janeiro have been engaged in favela occupation programmes over the past two years, the situation in Vila Cruzeiro is unique.
"This is really a big deal ... this is the first time ever, in Brazil's history, in the history of Rio, that the civil police have ever used any sort of these armoured personnel carriers in an operation such as this."
Six of the armoured vehicles entered the Vila Cruzeiro favela, where police say the drug gangs have taken refuge after they were forced out of 13 other slums.
The gangs are fighting back by opening fire on police stations and setting cars and buses ablaze, police said.
Our correspondent said that the violence that rocked Rio de Janeiro in recent days is a clear message from the drug traffickers.
"This is basically them saying, 'We're still here, we still can wreak havoc, we can still cause panic in the city'" Elizondo said.
Source: Al Jazeera and agencies