Activists have staged a symbolic burial of the Guanabara Bay, the sewage-filled Rio de Janeiro waterway where Olympic sailing competitions are to be held.

Saturday's demonstration was held on one of the city's most polluted beaches, Botagofo, which looks over the iconic Sugarloaf Mountain. The beach is dotted by plastic bottles and other household trash and enveloped in the sulfuric stench of sewage.

The protest's organizer, biologist Mario Moscatelli, said the event was among last-ditch efforts to force state authorities to keep their promise to clean up the bay before the Aug. 5-21 Olympics.

"This is an environmental crime," he said, after the protest that saw a mock coffin placed on the fetid sands, which were also draped with black cloth.