The glitter and glamour of Rio's stunning Olympics opening ceremony gave way Saturday to serious competition for the first medals of the Games dogged by a doom-laden buildup.
The first medal will be picked up in shooting on Saturday but hopes and dreams will also be fulfilled -- or shattered -- for cyclists, fencers, weightlifters, jodokas, swimmers, and archers as the first Olympic titles are determined.
Hours earlier, the Olympics were declared open at Rio's fabled Maracana stadium late Friday with Brazilian marathon runner Vanderlei Cordeiro lighting the cauldron following an exuberant display of Brazil's cultural heritage, capped by breathtaking pyrotechnics -- and a burst of high-octane samba.
The ceremony lifts the curtain on a more than two-week sporting festival featuring superstars like Michael Phelps and Usain Bolt.
All eyes will be on American swimming star Phelps, the most decorated Olympian in history, when he returns to the pool in the first week.
Track and field will see Jamaica's Bolt aim to defend his 100m, 200m and 4x100m crowns by clinching all three for the third straight Games.
Gymnastics could unearth a new heroine in America's teenage star Simone Biles, while rugby and golf return to the Olympic programme after gaps of 92 years and 112 years respectively.
But even the joys of the elite sports competition to come and the opening ceremony extravaganza failed to dispel gloom over Brazil's parlous political and economic situation, with boos and jeers breaking out as interim president Michel Temer declared South America's first Olympic Games open.
Temer took over when impeachment proceedings started against President Dilma Rousseff, whose supporters accuse him of plotting against the suspended leader.
The jeering ended only when it was drowned out by a loud barrage of fireworks.
- Lukewarm applause for Russians -
The opening ceremony followed fresh protests, when about 3,000 people waving signs saying "No to the Olympics!" gathered outside a luxury hotel where many athletes are staying.
Brazil has spent more than $10 billion (9 billion euros) on new infrastructure and preparations for the Games at a time of economic crisis, angering many Brazilians.
Despite the resentful undercurrent, and the protests against the Games just hours earlier, spirits were high among the athletes, performers, fans and officials at the 78,000-capacity Maracana.
"The Olympic dream is now a wonderful reality. The best place in the world is here and now," said organising committee chief Carlos Nuzman, to rapturous applause.
Brazilian singer Paulinho da Viola sang the national anthem to set off the show of laser lights and elaborate dances highlighting Brazil's history and rise as an emerging power.
Brazil's Gisele Bundchen strutted across the arena to the iconic "Girl From Ipanema" before Greece, home of the ancient Olympics, led out the colourful athletes' parade.
More than 10,000 athletes from 207 teams took part, with the biggest cheers reserved for the specially formed refugee team and the joyous Brazilian contingent.
Iran's flag bearer was Zahra Nemati, their first ever female flag-carrier who will compete in archery despite being paralysed in both legs.
The Russian delegation, battling allegations of state-backed doping, got only lukewarm applause when they entered the stadium.
Each athlete was presented with a seed and a cartridge of soil to enable them to plant a native tree of Brazil, which will ultimately form an "Athletes Forest" made up of 207 different species -- one for each delegation.
Indigenous tribes and dueling dance groups were among the highlights of a show low on technology but high on invention.
The evening's overwhelming theme was environmental protection.
An early opening sequence depicted the birth of life, culminating in the sprouting of a green entanglement of leaves from the stadium floor depicting the Amazon rainforest.
Indigenous Brazilians then performed dances before creating huge "Ocas" or native huts in the center of the stage.
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