Brazzaville - Nigeria outplayed Ghana 2-0 Wednesday in their opening 2015 All-Africa Games football match to reach the semi-finals in Brazzaville.
Junior Ajayi scored on 55 minutes at Stade de l'Unite in the Congolese capital and Kingsley Sokari added a second goal three minutes from time.
There are only three sides in Group B after Egypt withdrew rather than field a weakened team, and this enabled the Nigerians to secure a swift passage to the knockout stage.
Defending champions Ghana are in trouble with just one point from two matches and a minus-two goal difference.
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They hope Nigeria defeat second-place Senegal by at least three goals Saturday -- a result that would allow Ghana to squeeze through on goal difference.
Daniel Etor set up Ajayi for the deadlock-breaking goal and an exchange of passes with captain Azubuike Okechukwu created a chance for Sokari to score via an exquisite lob.
The under-23 tournament continues Thursday with Group A fixtures between Congo and Burkina Faso and Sudan and Zimbabwe.
Cameroon have won four of the previous 10 All-Africa Games football competitions, Egypt two and Congo, Nigeria, Algeria and Ghana one each.