Rio de Janeiro's homeless are being forced out of tourist areas in the middle of the night as the city hosts the Olympic Games, according to a Brazilian campaign group, but authorities said the homeless were being accommodated in shelters on a voluntary basis.

During the day, security forces have been offering to take some of Rio's estimated 5,500 homeless people to shelters far from Olympic venues, a spokesman for Project Ruas advocacy group said.

But late at night police are forcing homeless people out of the city's south zone, which is home to Copacabana beach and Olympic venues, the Rio-based group said.