Actress Angelina Jolie has talked about rape as a weapon of warfare at an African Union summit in South Africa.

The Hollywood star, who is also a United Nations special envoy on refugee issues, asked African representatives to support women's rights.

"Progress is slow, it is uneven, it is fragile and in some parts of the world it is being erased," she said.

"Think what it would mean if the 54 nations of the African Union press as one toward full rights and opportunities for women, not just for this great continent but for the world."

As co-founders of the Preventing Sexual Violence Initiative, Ms Jolie and former foreign secretary William Hague met with South African rights groups on Thursday to discuss strategies to prevent sexual violence.

South Africa has a high rate of rape and violence against women.