Oprah Winfrey said she was devastated and shaken to her core over complaints of sexual abuse made by girls at her South Africa academy.

Dormitory matron Tiny Virginia Makopo, 27, faces 13 charges of indecent assault, assault, and criminal injury following the alleged incidents at Winfrey's $40 million (£20m) school for disadvantaged girls.

Makopo appeared at a hearing in Johannesburg on Monday where she pleaded not guilty to the charges and was freed on bail. Her next hearing is December 13.

The Leadership Academy for Girls in Henley-on-Klip, near Johannesburg, was opened in January with a ceremony attended by the likes of President Nelson Mandela and singer Tina Turner.

At a press conference in Chicago, Winfrey - who previously revealed she was molested as a child - said she had spoken to all the alleged abuse victims and encouraged them to let their voices be heard in the investigation.

The media tycoon said: "This has been one of the most devastating, if not the most devastating, experience of my life."

She said the situation was "horrible" and the academy was moving forward to create a "safe, open and receptive" environment for the girls.

Winfrey said she had promised to buy mobile phones for all the girls involved, and given them her personal number so they could phone her with any problems or questions in the future.

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