Cricket South Africa (CSA) have admitted that they were "surprised" by captain Graeme Smith's decision to retire from international cricket.

Smith announced that the ongoing third Test against Australia will be his final outing for the Proteas, signalling an end to an illustrious career for the batsman.

CSA chief executive Haroon Lorgat admitted that he wasn't expecting the news, but was keen to pay tribute to the most successful Test captain in the history of the sport.

"Although Graeme's decision to retire from all forms of international cricket comes as a surprise to all of us, we must respect him for deciding to call time. Knowing him as well as I do, having been instrumental as a selector in appointing him as a young captain, he would not have taken this decision lightly or without a great deal of thought," Lorgat told CSA's official website.

"He has captained the Proteas for more than a decade and he will draw a lot more satisfaction from the fact that he leaves our Test team at the top of the world and in such good health rather than from all the personal records he has achieved as the longest-serving captain the game has ever seen in the demanding Test format.

"He can leave the game with pride and he thoroughly deserves the gratitude of our nation for leading the Proteas with much distinction. From a personal point of view I am thrilled that I was part of the panel that appointed him captain in 2003 when his first major assignment was a tough tour to England and I feel privileged to see him now move on to the next stage of his career. He has been a mighty warrior, a leader of men and an exceptional part of our international cricket."

Smith has made 17,228 runs over all formats for South Africa.