The fire broke out around 6 p.m. local time (2100 GMT) on Morro dos Cabritos, a massif made up of rocks and vegetation located between Copacabana and the Rodrigo de Freitas lagoon, in the tourist region of southern Rio, near the beach.
The flames, which according to the local press were visible from other neighborhoods such as Ipanema, did not affect inhabited areas, but only vegetation, a spokesman for the fire department told AFP.
From a street at the foot of the hill, at the exit of one of the Copacabana tunnels, several hearths consuming trees and bushes growing on the rocky surface were visible, noted an AFP photographer.
At least three brigades have been deployed to the site to try to contain the fire, the cause of which is still under investigation.
In 2010, four hectares of Morro dos Cabritos went up in smoke after a fire caused by the fall of a sky lantern.