Barcelona forward Neymar was unable to help Brazil make a winning start to the Rio 2016 Olympic Games as the hosts were held to a goalless draw by 10-man South Africa in Brasilia on Thursday.
Elsewhere, South Korea thumped Fiji 8-0 - scoring three times in 90 seconds during the second half.
Nigeria, who arrived in Brazil just six hours before their opening match against Japan kicked off, won 5-4.
Striker Oghenekaro Etebo scored four times for the African side.
Group A - which features Brazil and South Africa - is a four-way tie after Iraq and Denmark also drew 0-0 in front of a sparse crowd inside the Estadio Nacional Mane Garrincha.
Brazil, who were booed off by some of the crowd, had the best chance of their game but new Manchester City forward Gabriel Jesus hit the post from two yards out.
South Africa’s Mothobi Mvala was sent off just before the hour after being shown a second yellow card but the London 2012 runners-up could not find a breakthrough.
The men’s football tournament started one day before Friday’s opening ceremony because of a packed schedule.
Group B started with an entertaining 2-2 draw between Sweden and Colombia.
The South Americans took the lead through Teofilo Gutierrez before goals from Mikael Ishak and Astrit Ajdarevic put Sweden in front.
A penalty from Dorlan Pabon ensured the points were shared.
Defending champions Mexico were held to a 2-2 draw by Germany in Group C.
The Mexicans took the lead early in the second half through Oribe Peralta but Arsenal midfielder Serge Gnabry levelled soon after.
Rodolfo Pizarro swept Mexico into the lead again but Matthias Ginter, part of Germany’s 2014 World Cup-winning squad, powered home a late header to earn his side a point.
Portugal made a winning start in Group D as they beat Argentina 2-0 at the Olympic Stadium in Rio de Janeiro.
Porto striker Goncalo Paciencia opened the scoring midway through the second half, firing home from outside the box.
A goalkeeping error by Geronimo Rulli gifted Portugal a second as he let Pite’s tame shot squeeze through his legs.
The other match in that group saw Honduras hold on to beat Algeria 3-2.
The Central American team had a 2-0 lead at the break thanks to goals from Romell Quioto and Marcelo Pereira.
Algeria pulled one back through Sofiane Bendebka before Anthony Lozano re-established the Hondurans’ two-goal lead, before Baghdad Bounedjah’s late consolation.
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