U.S. first lady Michelle Obama will visit Thursday the Robben Island prison where former South African President Nelson Mandela was jailed for 18 years.

The first lady met with Mr. Mandela at his home in Johannesburg Tuesday, at the beginning of her two-nation tour of southern Africa.

On Wednesday, Mrs. Obama delivered an emotional address to an enthusiastic group of young women at Soweto's historic Regina Mundi Church, a center of South Africa's anti-apartheid movement.

She urged young Africans to take leadership roles in their countries and unite to shape a better future for the continent.

Mrs. Obama, America's first African-American first lady, said Africa's youth are heirs of a generation who have sacrificed much to attain independence and freedom.

She said America is looking to Africa's young people to transform economies, end corruption, hold free and fair elections, stop the stigma of AIDS, and ensure women are not treated as second-class citizens.

The speech was part of a U.S.-sponsored forum for young female African leaders.

After the address, Mrs. Obama visited a museum and did community service in Soweto.

Mrs. Obama is traveling without her husband on her two-nation tour of southern Africa. She is joined by her daughters, Malia and Sasha, and other relatives.

The first lady will travel to Botswana on Saturday for a two-day visit there.