Brazil and superstar Neymar were booed off as their quest for a maiden Olympic football gold medal began with a 0-0 draw against 10-man South Africa on Thursday.

Barcelona ace Neymar is by far the biggest name in the competition and has been tasked with restoring pride to Brazilian football after a catastrophic 7-1 semi-final defeat to Germany on home soil at the 2014 World Cup.

However, he endured a frustrating afternoon on a sandy and slow surface in Brasilia as South Africa held out despite Mothobi Mvala's red card half an hour from time prompting the crowd to jeer the hosts off on the final whistle.

"For us the draw is a defeat," said Neymar.

"The team went on the field to win, we know our responsibility, we know it isn't going to be easy.

"It is not just a case of turning up and winning the gold medal."

Group A is now in a four-way tie on one point after Iraq and Denmark also played out a scoreless draw.

In contrast to the swaths of empty stands across the six cities being used to host the men's and women's football tournaments on the opening two days, the hosts commanded a near-capacity 70,000 crowd.

However, the Brazilian side boasting Neymar, Manchester City's new £27 million ($35.4 million) signing Gabriel Jesus and Marquinhos of Paris Saint-Germain did not provide the expected victory procession.

South Africa's Lebo Mothiba had a host of chances to cause an almighty upset, but failed to make a ragged Brazilian defence pay for early nerves.

"The first game is always the most difficult due to the anxiety of the competition starting," added Neymar.

"I think the anxiety hurt us a bit."

Neymar proudly sported the captain's armband and had Brazil's best two efforts of the first half with strikes from outside the box that forced South African 'keeper Itumeleng Khune into stunning saves.

And Khune said he would tell his grandchildren of the day he stopped the Barcelona star.

"I am so happy to make my appearance, make my mark," said Khune.

"Definitely my grandchildren will watch the DVD of this match."

South Africa dominated the early stages of the second half with Mothiba and captain Keagen Dolly coming close.

But their chances appeared to have gone when defender Mvala was sent off for two quickfire yellow cards.

Brazil ramped up the pressure. Jesus somehow turned the ball onto the post with the goal gaping, whilst a dipping drive from Neymar landed on the roof of the net.

However, South Africa resisted to add problems on the field for the hosts to a Games build-up already marred by fears surrounding the Zika virus and Brazil's political turmoil.

Portugal's stunning summer after winning Euro 2016 could get even more golden as they saw off Argentina 2-0 to the delight of the Brazilian crowd in Rio.

Both sides are looking to the future with Lionel Messi having announced his international retirement with Argentina after three final losses and Portuguese hero Cristiano Ronaldo now 31.

Gonzalo Paciencia's low drive put Portugal ahead before a horrible error from Argentina goalkeeper Geronimo Rulli allowed Pite's long-range effort to sneak between his legs to secure the three points six minutes from time.

Honduras beat Algeria 3-2 in the other Group D game.

Germany played out a entertaining 2-2 draw with 2012 gold medallists Mexico under a torrential downpour in Salvador.

Three goals in 10 minutes in the second half put Mexico 2-1 ahead as Oribe Peralta and Rodolfo Pizarro struck either side of Arsenal's Serge Gnabry's reply for Germany.

However, the only World Cup winner on show at the Olympics Matthias Ginter, who flew 20,000km from Borussia Dortmund's pre-season tour in China to Brazil, earned Germany a point.

South Korea smashed Fiji 8-0 in the other match in Group C with Ryu Seung-Woo scoring a hat-trick.

Nigeria arrived in the Amazonian city of Manaus just hours before a thrilling 5-4 win over Japan as the original plane intended to take them from their training base in Atlanta on Wednesday was deemed "too small" for the squad and staff.

The delay didn't seem to affect the 1996 gold medallists as four goals from Oghenekaro Etebo edged a memorable nine-goal thriller.

Sweden and Colombia drew 2-2 earlier in Manaus in Group B.