Gyan was tripped inside the box for a penalty which was converted by Andre Ayew on 32 minutes.
Up next is Mali, who put up a brave performance to draw 0-0 with Egypt, on Saturday at Port Gentil.
Ghana’s final match will be against Egypt on 27 January at the same.
Gyan says he and his teammates are ready for any opponent at the tournament.
“Mali and Egypt? We are not interested about our opponents,” Gyan said after the game.
“We are looking to win all our games to top the group.”