There was no official update Tuesday morning on the 94-year-old Mandela. The government has previously said he is in serious but stable condition.
A foundation led by retired archbishop Desmond Tutu has described Mandela as an "extraordinary gift" and offered prayers for his comfort and dignity.
Mandela, leader of the anti-apartheid movement, spent 27 years in prison during white racist rule. He was freed in 1990, and then embarked on peacemaking efforts during the tense transition that saw the demise of the apartheid system and his own election as South Africa's first black president in 1994. He's in a hospital in Pretoria, the capital.