Hosts France secured a second straight victory as Kiliann Sildillia struck for a 1-0 success over Guinea, while Spain and Japan reached the quarterfinals in the second matchday of the men's Olympic soccer tournament on Saturday
France struggled to find their feet in Bordeaux after their opening 3-0 Group A triumph over the United States but found a way past a solid Guinea team, who had two efforts disallowed in the first half, with Sildillia's brilliant 75th minute header.
Sildillia brought relief to French fans when he connected with Michael Olise's fine cross to send the crowd into raptures.
Spain clinched a spot in the quarterfinals with their second Group C win by beating the Dominican Republic 3-1, while Argentina defeated Iraq by the same scoreline in Group B.
Argentina recovered from their chaotic opening loss to Morocco and boosted their chances of reaching the last eight as they moved top of their group on goal difference.
Javier Mascherano's Argentina side opened the scoring in Lyon after 14 minutes thanks to a Thiago Almada volley but Iraq equalised with Aymen Hussein's header seconds before half-time.
Substitute Luciano Gondou's header in the second half and a superb strike by Ezequiel Fernandez six minutes from time secured all three points for the 2004 and 2008 gold medallists.
"It was a difficult match. Iraq are a physically strong team. The only thing we needed to do was win, it's a great relief," Mascherano said.
"We struggled but in the second half we found a lot of inside play and finishing on the outside."
Earlier in Bordeaux, Spain dominated the Dominican Republic from the early stages and went ahead in the 24th through Fermín López. However, the debutants equalised as Angel Montes de Oca scored the first Olympic goal for the country.
Alejandro Baena and Miguel Gutiérrez sealed the win over the Dominicans, who were reduced to 10 men before half-time after Edison Azcona's red card.
The United States scored three times in 30 minutes in a crushing 4-1 victory over Group A rivals New Zealand in Marseille, while Paraguay netted twice deep in stoppage time to beat Israel 4-2 in their Group D clash at Parc des Princes.
Also in Group D, Mali missed a late penalty and could not avoid losing 1-0 to Japan, who have qualified for the last eight having also thrashed Paraguay 5-0 in their first game.
Uzbekistan crashed out of their first Olympics following a 1-0 loss to Egypt in Nantes after a goal by Ahmed Koka in their second Group C fixture.
In Group B, 10-man Ukraine claimed a dramatic 2-1 win over Morocco in St Etienne thanks to Ihor Krasnopir's late winner.