ANC calls for calm as Mandela has tests in hospital

South Africa's governing African National Congress has appealed for calm over speculation about the health of Nelson Mandela, who is undergoing medical tests in a Johannesburg hospital.

Friends and family, including Mr Mandela's ex-wife, Winnie, have been visiting him. The 92-year-old former South African president, is said to be increasingly frail.

Andrew Harding reports.