Nigeria, Afcon runners-up in 2023, join Egypt as the second side through to the knockout stage, but both coach Eric Chelle and their supporters will feel relieved after what looked set to be a comfortable last quarter of an hour turned into a nervy finish.
Both sides had won their opener in Morocco, with Tunisia cruising past Uganda and Nigeria edging past the Tanzanians in a hard-fought encounter.
Osimhen had a goal ruled out for offside before the Super Eagles striker opened the scoring on the stroke of half-time, expertly guiding a header between two Tunisian defenders and into the bottom-right corner from Lookman’s inviting left-wing cross.
The Super Eagles doubled their advantage early in the second half, as Ndidi picked a good time to score his first international goal when he rose highest to power home a header from Lookman’s corner.
Osimhen teed up former England youth international Lookman for the third, but Talbi steered his header past Nigeria goalkeeper Stanley Nwabali to reduce the deficit.
Tunisia were handed a lifeline when a looping cross dropped onto the forearm of Osayi-Samuel, and Malian referee Boubou Traore awarded a spot-kick after being sent to his pitchside monitor by VAR.
Abdi smashed home, but the 2004 champions ultimately fell short of a stirring comeback.
Tunisia remain well placed to join the West Africans in the next round, with a draw against Tanzania enough to progress – and their manager Sami Trabelsi will be keen to avoid a repeat of the 2013 Afcon, when a group-stage exit ultimately led to his resignation as coach.
