
Defending champions Egypt beat the Ivory Coast 4-1 in Kumasi through a brace by Amr Zaki and goals by Ahmed Fathi and Mohamed Aboutrika, while Abdelkader Keita pulled one back for the Ivorians.
For Cameroon, who beat the hosts Ghana 1-0, Mexican-based substitute Alain Nkong scored the only goal of the game in the 71st minute.
In Kumasi, Ivory Coast dominated the early spell of their game, but it was Fathi who gave his side the lead in the 12th minute with a long range effort that took a wicked-deflection off Salomon Kalou.
Worse was to follow for the Elephants as goalkeeper Boubacar Barry had to be substituted with an injury. In his place German-born Stephan Loboue came on.
The match came to life midway through the second half as three goals were scored in the space of five minutes.
The Pharaohs doubled their lead in the 62nd minute as Zaki scored with a header after Ahmed Hassan's corner was flicked on by Ivorian defender Didier Zokoro.
It took the West Africans just a minute though to hit back through Keita, whose powerful shot from outside the area gave Essam Al Hadari, who earlier pulled off two world class saves to deny Didier Drogba, no chance.
Al Hadari, said that he was pleased his side had managed to beat the Ivory Coast, even though they had so many good players in top leagues throughout Europe.
"This is a great victory and now we want to go all the way and win the cup again, like we did last time."
But any hopes Ivory Coast had of coming back were effectively killed off in the 67th minute as Ivorian defender Kolo Toure was left stranded by Zaki who entered the area and shot past Loboue from 11 metres.
Mohamed Aboutrika added a fourth in injury time as he was fed a ball in front of the goal by substitute Mohamed Zidan.
In the earlier game in Accra, the 46,000 seater Ohene Djan stadium was surprisingly not filled to capacity, with some 12,000 seats empty at the start of the game. Although many of them filled during the course of the first half, at least 3,000 empty seats remained.
Ghana coach Claude le Roy had to substitute winger Laryea Kingston, who injured his ankle during the warm-up. In his place Abedi Pele's son Andre Ayew came in to the side for his first start of the tournament.
The Frenchman also had to replace suspended captain John Mensah, taking Chelsea midfielder Michael Essien into the backline instead and giving him the captains' armband.
The first chance of the game fell to the Black Stars in the fifth minute as Sulley Muntari's free-kick floated through the Cameroon goalmouth, only for Eric Addo just failing to connect with the ball.
Ayew had the next chance on 27 minutes after being set up by Quincy Owusu-Abeyie, but the Olympique Marseille forward who went around two defenders, shot too weak to really trouble Idriss Kameni.
Cameroon came close to opening the scoring in the 37th minute when a free-kick from Geremi Njitap from all of 35 metres hit the post.
The hosts pushed forward in the opening spell of the second half, with the crowd urging them on everytime they crossed into the Cameroon half.
Somewhat against the run of play the Indomitable Lions took the lead in the 71st minute as four quick passes saw the ball landing in the back of the Ghana net.
Substitute Joel Epalle played the ball to Alain Nkong, who laid it back to Samuel Eto'o. The Barcelona striker played a through ball back to Nkong, who had already started a run into the area.
The striker, who plays for Atlante in Mexico, unleashed a powerful shot that gave Richard Kingson no chance.
Ghana came agonizingly close to scoring an equalizer in the 80th minute when Muntari's free-kick found Junior Agogo in the area and his powerful header went just over the crossbar.
Cameroon's coach Otto Pfister said that he will be able to find a suitable replacement for defender Andre Bikey, who was sent off in injury time after he pushed over a medical official, who was trying to hurry an injured Cameroon player off the field.
As Bikey tried to leave the field, he was met with a barrage of water bottles thrown from the stands.
"He is a very good player, but I have enough players in my squad to be able to replace him. I am sure we will have a good team for the final."
The final is a replay of both teams' opening group game, which Egypt won 4-2 after an excellent first-half performance saw them go into the change rooms 3-0.
Ghana and the Ivory Coast will play in the Third Place play-off on Saturday in Kumasi.
By Peter Auf der Heyde, dpa