"Our thoughts and prayers are with the family of Lady Thatcher and the people of the United Kingdom during this difficult time," he said.
Baroness Thatcher served as prime minister from 1979 to 1990. She was the first woman to hold the post.
The ANC said Thatcher redefined British politics.
"Her passing signals the end of a generation of leaders that ruled during a very difficult period characterised by the dynamics of the Cold War," ANC spokesman Jackson Mthembu said in a statement. "Her tenure as Prime Minister redefined British politics and public administration and these impacted greatly on the European politics and governance.
"She was one of the strong leaders in Britain and Europe, to an extent that some of her policies dominate discourse in the public service structures of the world.
"The ANC extends its condolences to her family, her loved ones and the people of Britain. May her soul rest in peace."
Thatcher refused to recognise the ANC during apartheid.
She died yesterday following a stroke. She was 87.
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