Authorities say the "eco-barrier", which will encircle part of the famous Dona Marta favela in the southern part of the city, is intended to protect the nearby Atlantic rainforest from illegal occupation as well as improve security and living conditions for residents.
"This is something that is very similar to what Israel does to the Palestinians and to what happened in South Africa," said Mauricio Campos, from the Rio human rights group Network of Communities Against Violence.
He said a wall would serve only to "segregate" slum residents from the rest of society.
The wall is expected to be completed by the end of this year and, according to reports in the local press, may be followed by similar barriers around Rio's other favelas.
In a statement, the state governor, Sergio Cabral, who ordered the "eco-limit" fence to be built, said it was part of moves by his administration to improve living standards and protect slum residents from the armed gangs that control many of Rio's 700 or so favelas, with an estimated 2.5 million population out of a total 10 million.
"What has happened in Rio de Janeiro over the last two decades has been the passivity of authorities in relation to the uncontrolled growth of the slums," he said. Such walls would, Cabral said, help the city deal with "drug trafficking and vigilantes, by putting limits on uncontrolled growth".
Dona Marta is home to an estimated 7,500 people. The favela was the setting for an award-winning documentary about cocaine by the British film-maker Angus Macqueen, as well as a 1996 Michael Jackson music video directed by Spike Lee.
Jackson's producers were forced to negotiate access with the local drug traffickers. Since last November, however, the shantytown has been under 24-hour police occupation as part of a state government initiative to make Dona Marta a "model favela". In December, Rio's security secretary boasted that the slum was "free from the law of the rifle."
The pilot project aims to rid the favelas of traffickers using a mixture of military force and "hearts and minds" community policing.
Silvio dos Santos Ferreira, member of a Dona Marta residents association attacked the idea of the wall saying that the "alleged environment protection" is nothing else but an "Israeli type policy" like that applied with the Gaza Wall.
"It's nothing else but a system to segregate and further discriminate against the poor people of the city," he added.
Mercopress