Imraan, who plays for the KwaZulu-Natal provincial team, and pacer Wayne Parnell are the two new faces in the squad.

Imraan and Parnell replace Neil McKenzie and Morne Morkel, who have been dropped from the squad.

South African vice-captain Ashwell Prince, who was dropped for the first two Tests because of injury, replaces Smith, who is nursing an injured right hand.

CSA Selection Convenor Mike Proctor made the announcement soon after South Africa was trounced by Australia in the second Test in Durban, giving the visiting side 2-0 lead.

Proctor said Imraan deserved to be selected in the squad.

"Imraan Khan fully deserves his chance. He scored his third century of the season in the SuperSport Series at the weekend -- the only player to do so -- and is the only batsman to have scored more than 600 runs with an average just above the 60 mark," said Proctor.

A 15-man Twenty20 squad was also announced for the two matches that will follow the Test series. The South African T20 side will be led by Johan Botha.

The Test squad: Ashwell Prince (capt), Hashim Amla, Mark Boucher, A B de Villiers, J P Duminy, Paul Harris, Jacques Kallis, Imraan Khan, Albie Morkel, Makhaya Ntini, Wayne Parnell, and Dale Steyn.