Graça Machel, the activist, campaigner and widow of Nelson Mandela, has urged South Africans to break the cycle of violence that women and girls are subjected to.

She was giving a speech to mark the 90th birthday of Nobel peace prize winner and South Africa's anti-apartheid icon Desmond Tutu.

"Violence is the breast milk we feed our young," she said in a message to South Africans and urged them to honour and cherish Archbishop Tutu's legacy by ensuring relationships are based on respect and equity.

She spoke of the high incidence of teenage pregnancy in the country.

She said more needed to be done to identify and punish incidents of rape, sexual coercion and abuse as well as incest.

She said children were growing up experiencing hostility and exploitation and it was time for South Africans to stop passing on their trauma to the next generation.