Tunisia capitalised on a wasteful Moroccan performance to beat their North African rivals 2-1 in Group C.
Khaled Korbi opened the scoring for the Carthage Eagles, floating a free-kick straight into the Moroccan goal.
Substitute Youssef Msakni doubled Tunisia's lead with a wonderful solo effort, before Moroccan skipper Houcine Kharjah pulled one back.
Morocco squandered several chances to score but Tunisia deserved their opening win, after a gutsy performance.
The Atlas Lions started well and created opportunities from the outset, with Mbark Boussoufa busy trying to link up with Arsenal's Marouane Chamakh up front, who found space but shot straight at Aymen Mathlouthi in the Tunisian goal.
That miss would set the tone of much of the game, with Mathlouthi pulling off a string of saves from the Moroccan attackers.
Tunisia weathered the opening exchanges well before capitalising and opening the scoring through Korbi's free-kick on 34 minutes.
Korbi floated in a dangerous ball from well outside the area which nestled in Morocco's net, after Saber Khelifa did enough to distract Nadir Lamyaghri in the Moroccan goal.
Morocco had two quick opportunities to equalise, with Younes Belhanda shooting just wide after a good run into the area, and then Chamakh almost latched onto a looping ball, but again Mathlouthi did enough to put him off and clear his lines.
Moroccan coach Eric Gerets responded by introducing Adel Taraabt for Oussama Assaidi at the break, and the QPR striker was involved in the action straight away, drawing yet another save from Mathlouthi.
Youssouf Hadji followed Taraabt onto the field but missed horribly, after collecting the ball beautifully in the box, and blasting high and wide.
The miss would cost Morocco once more as Msakni danced through their defence and shot across Lamyaghri's goal for his first goal for his country, on 76 minutes.
Morocco finally responded 10 minutes later, pulling one back through captain Kharjah, who headed in from close range after Ahmed Kantari's headed flick back in front of goal.
And Kharjah was unlucky not to double his tally and bring Morocco level as he created space for himself well in the box, only to shoot just over.
But Tunisia held out well and deserved to edge their neighbours, in a fascinating encounter in Libreville.