Gabon and Switzerland failed to take advantage of Mexico and South Korea's 0-0 draw earlier today as they were forced to share the points after a 1-1 draw.
Switzerland made the perfect start to their Olympic campaign by taking the lead within six minutes when Admir Mehmedi slotted home a penalty.
Gabon almost equalised after 23 minutes when Jerry Obiang hit the post with an effort before Levy Madina squandered a good chance of his own as the West African side pushed for an equaliser.
The leveller came right on the stroke of half-time through Pierre Aubameyang, who coolly slotted the ball past Diego Benglio in the Switzerland goal to send the two sides into the break at 1-1.
The second half was less eventful than the first, with the major talking point coming with 12 minutes left as Switzerland's Oliver Buff was shown a second yellow card.
With all four teams in Group B tied on one point apiece, next up for Gabon is Mexico, while Switzerland will face South Korea.