With a limited budget, the consequence of a biting recession that roiled preparations for South America's first Olympics, Brazil laced its high-energy opening party for the games of the 31st Olympiad with a sobering message of the dangers of global warming.

Graphic projections of world cities being swamped by rising seas set Rio de Janeiro's otherwise fun and festive gala apart from the more self-congratulatory and lavish celebrations that Beijing and London wowed with in 2008 and 2012.

Brazilian police arrested a Moroccan Olympic boxer on Friday for allegedly sexually assaulting two female cleaners in the athletes' village in Rio de Janeiro.

Officers arrested Hassan Saada, 22, from Casablanca, on suspicion of committing the assault on Wednesday, said a police statement released hours ahead of the Games' opening ceremony.

The Olympic flame wound its way around Rio de Janeiro's iconic landmarks on Friday as protesters unleashed a fresh blast of anger ahead of the opening ceremony of the trouble-plagued sporting spectacle.

The carnival capital of the world is hoping Friday's extravaganza at the Maracana Stadium will draw a line under a turbulent seven-year build-up dogged by recession, rising crime and doping scandals.

FIFA's ethics committee on Friday cleared president Gianni Infantino of ethics violations after investigating him over his use of private jets, personal expenses, hiring methods and a contract dispute.

Silvio Berlusconi agreed Friday to sell AC Milan to Chinese investors under a deal set to end his trophy-laden three decades in charge of the Italian giants by the end of this year.

Disgraced former FIFA president Sepp Blatter has admitted his six-year ban from all football-related activity has taken a toll on his mental health.

The Olympic torch approached the end of its nationwide relay around Brazil on Thursday, the day after police clashed with demonstrators and with new political protests planned for the opening ceremony.

The torch, meant to be a symbol of hope and unity, has had a troubled 12,400 (20,000 km) journey around Brazil, featuring attempts to put out the flame with buckets of water, the shooting dead of a rare, captive jaguar, and violent protests by Brazilians angry at the cost of the Games.

Presidents from France and Hungary, Italy's prime minister and the U.S. secretary of state headed for Rio on Thursday to step up their countries' bids for the 2024 Olympics.

Budapest, Los Angeles, Paris and Rome are in contention to stage the 2024 Games and the Rio Games will be a key campaign stage ahead of the International Olympic Committee vote in September next year.

IOC president Thomas Bach said the final Russian team for the Rio Olympics would only be known later Thursday as IOC officials rush to complete doping checks.

The first sporting action of the 2016 Olympics started in a virtually empty stadium on Wednesday as the Russian doping scandal rumbled on.

With the formal opening ceremony at the Maracana stadium just two days away, the women's football tournament started with a game between Sweden and South Africa.