Harare - Zimbabwe's opposition leader Morgan Tsvangirai has cancer of the colon and began chemotherapy this week, he announced on Monday.
Ending weeks of speculation, Tsvangirai, 64, said doctors in South Africa last month operated on him - successfully - but that was only the "first of several medical procedures" he would have to undergo.
In a dig at President Robert Mugabe, the Movement for Democratic Change leader said it was his "firm belief" that "the health of national leaders, including politicians, should not be a subject of national speculation and uncertainty."
Mugabe, 92, travels frequently to Singapore for medical attention for what two years ago was officially put down to cataract treatment. A fuller explanation has never been given.
Speculation had swirled over Tsvangirai's state of health after he failed to attend an MDC march in the eastern city of Mutare last week.
Thanking his wife for her "love and caring" Tsvangirai said: "I intend to confront this development with the determination to overcome it."
Tweeted political analyst @PedzisaiRuhanya: "You are a brave and open person. Bravo".