Against the run of play, Tunisia bounced back and probed for a goal but the lanky Mngonyama was equal to the task despite nearly conceding a corner kick.
In the dying minutes of the first half, Abbubaker Mobara unleashed a powerful shot from a set piece but it was cleared and Dolly's follow-up attempt was safely collected by Sabri.
Upon their return from the tunnel, the Tunisians came back stronger and were rewarded with a corner but Mngonyama was again ready to clear the danger.
Towards the 70th minute, Da Gama introduced Phakamani Mahlambi of Bidvest Wits for Black Leopards’ Siphelele Ntshangase and a few seconds later, Mobara saw his set piece flying over the woodwork.
After 80 minutes of action, both sides failed to create clear cut chances but it was Motupa who nearly scored after he broke free, but he lacked composure and missed a golden opportunity.
However, with five minutes to go, Menzi Masuku grabbed his second goal of the tournament when he received an assist from the enterprising Mahlambi. The Orlando pirates man sent the South Africans through to the semis.
Da Gama’s men join the hosts and winners of the group, Senegal, who beat Zambia in the other match, in the semis.
February, Mngonyama, Coetzee, Moerane, Mobara, Dolly, Motupa, P. Ntshangase (Mahlambi 60’), S. Ntshangase, Masuku (Rikhotso 89’), Mekoa
Ben Sabri, Kechrida, Kchok, Mechan, Yassine, Jelassi, Khelil, Abd (Jaibi 64’), Jouini, Ghandri, Mansour