US President Obama: Mandela a hero for the world

US President Barack Obama, who is on a visit to Africa, has said Nelson Mandela is a hero to him, and a "hero for the world".

Speaking in Senegal, he said: "Our thoughts and prayers right now are with the people of South Africa and more specifically the Mandela family."

He added: "His legacy is one that will linger on throughout the ages."

Mr Mandela remains in a critical condition in hospital in Pretoria, where he has been since 8 June with a lung infection.