Brazil face another embarrassing exit from a tournament on home soil after Neymar slumbered through a second 0-0 draw of Rio 2016 against Iraq.

The Olympic hosts need to beat group leaders Denmark on Wednesday to win to avoid a stunning exit, just two years after their devastating 7-1 World Cup defeat by Germany.

Neymar was expected to ease Brazilian football's wounded pride by delivering a first ever Olympic gold for the five-time world champions.

However, the Barcelona star was eclipsed. And just as in their opening stalemate against South Africa, Brazil were booed from the field in Brasilia on Sunday as they paid for their profligacy in front of goal.

Portugal and Nigeria were the first sides to seal their places in the quarter-finals with victories over Honduras and Sweden respectively.

There were also wins for Argentina, Denmark and Mexico.

In contrast to his display against South Africa when he was labelled "greedy", Neymar was a peripheral figure against Iraq and lost his cool when he fired the ball at Sherko Kareem in the second-half as the Iraqi prevented him from taking a quick free-kick.

Caught dozing

Manchester City's £27 million ($36 million) signing Gabriel Jesus had another night to forget. After claiming he "wouldn't sleep" after missing an open goal against the South Africans, he skewed an golden chance wide inside two minutes before being hooked off by coach Rogerio Micale early in the second-half.

Iraq could even have snatched a shock win when Mohanad Abdulraheem's first-half header came back off the inside of the post.

Renato Augusto had Brazil's best chance when he shot over the gaping goal deep into seven minutes of stoppage time.

Romanian referee Ovidiu Hategan waived away strong claims for a penalty moments later when Gabriel Barbosa tumbled inside the area.

Atletico Madrid's Angel Correa scored and set up Jonathan Calleri's winner as 10-man Argentina got their challenge for a third Olympic gold back on track with a 2-1 win over Algeria in Rio.

Argentina coach Julio Olarticoechea was put in charge for the Games just weeks before their opening 2-0 defeat to Portugal. Olarticoechea took over from Gerardo Martino who quit after a second Copa America final defeat to Chile in as many years.

Olarticoechea's options were slashed by a number of high-profile pullouts and European clubs not releasing their players so close to the start of the season.

However, it was Calleri, called in at the last minute to replace Luciano Vietto, who bundled home the winner 20 minutes from time.

Argentina still need to beat Honduras in their final Group D game on Wednesday to qualify for the quarter-finals.

Portugal are assured of their place in the last eight after beating Honduras 2-1.

Goals from Tobias Figueiredo and Goncalo Paciencia cancelled out Alberth Elis's first minute opener.

World champions Germany also dug themselves out of trouble as a stoppage-time equaliser from Arsenal winger Serge Gnabry salvaged a thrilling 3-3 draw against South Korea in Salvador.

Germany lie in third place in Group C, two points behind Mexico and South Korea.

They face the prospect of having to beat Fiji by at least four goals in their final group game to progress, if South Korea's final match with Mexico also ends in a draw.

Defending champions Mexico needed a second-half fightback to stave off one of the biggest shocks in Olympic football history to beat Fiji 5-1.

Fiji benefited from New Zealand's disqualification for fielding an ineligible player to qualify for the Olympics at last year's Pacific Games. They were thrashed 8-0 by South Korea on their debut on Thursday.

However, they led 1-0 at half-time in Salvador thanks to Roy Krishna's opener.

Erick Gutierrez was Mexico's saviour as he struck four times in the second-half.

Sadiq Umar headed 1996 winners Nigeria into the quarters with a 1-0 win over Sweden.

Colombia hold a one point advantage over Japan and Sweden in the fight for second place after their second 2-2 draw against Japan in the Amazonian city of Manaus.