Reigning champions Canada got a lifeline at the Paris Games following a 2-1 last-gasp win over hosts France, while Spain and the United States claimed wins to reach the quarter-finals on the second matchday of Olympic women's football on Sunday.
Canada's quest to defend their 2021 gold medal was marred following a drone spying scandal that led to a year-ban of coach Bev Priestman and a six-point deduction by world governing body FIFA from the Olympic tournament.
The top two teams in each three groups advance, along with two best third-placed sides, leaving Canada, now led by assistant coach Andy Spence, needing maximum points in their remaining Group A matches, on top of a favourable goal difference.
The slim Canadian hopes seemed to be dashed after France's Marie-Antoinette Katoto struck in the 42nd minute following a neat passing move.
But captain Jessie Fleming equalised 13 minutes after the break. The match looked to be heading for a draw before Vanessa Gilles seized on a rebound from the goalkeeper in the 12th minute of stoppage time to fire home.
Canada face Colombia in their final group match on Wednesday.
Four-time Olympic gold medallists US carried on their good form in Group B and secured a 4-1 emphatic win over Germany in Marseille, thanks to a first-half brace from Sophia Smith and goals from Mallory Swanson and Lynn Williams.
Smith gave Emma Hayes' side an early lead with a simple finish in the 10th minute, before Giulia Gwinn equalised for the 2016 Olympic champions.
Swanson, who scored a quick-fire double in the win over Zambia, made it 2-1, while Smith's deflected goal before halftime and Williams' late effort sealed the rout.
Earlier, world champions Spain secured a spot in the next round with a 1-0 win over Nigeria in Nantes, courtesy of Alexia Putellas' late winner.
The world champions had to wait until the closing stages in their Group C clash to break the Nigerian wall with a wonder free-kick from former Ballon d'Or winner Putellas.
The Barcelona midfielder struck in the 85th beyond the Nigerian goalkeeper and defenders, who until then had frustrated Montse Tome's side.
Also in Group C, Brazil missed the chance to progress after a late 2-1 loss to Japan at Parc des Princes.
Brazil were leading after the break with Jheniffer's low shot in the 56th minute after a play created by six-time Olympian Marta, who left the pitch to a standing ovation in the 84th minute.
Japan claimed victory with two stoppage-time efforts by Saki Kumagai's from the penalty spot and substitute Momoko Tanikawa from long range after a misplaced pass by Rafaelle.
Australia and Colombia boosted their chances of making it to the next round with their first wins in the competition.
In a goal feast in Nice, the Matildas rallied from two goals down to clinch a stunning 6-5 win over Zambia in Group B, with Australian Steph Catley and Zambia's Racheal Kundananji scoring doubles, while Barbara Banda netted a hat-trick, the third to her name for an Olympic record.
Colombia edged Group A rivals New Zealand 2-0 in Lyon thanks to Marcela Restrepo's volley and a fine goal from Leicy Santos.