Officials in South Africa say former president Nelson Mandela spent the night in a Pretoria hospital, where he was admitted to undergo tests.

President Jacob Zuma visited Mr. Mandela Sunday morning, and said the Nobel Peace Prize laureate was “comfortable, and in good care.”

An earlier statement from Mr. Zuma's office Saturday said the 94-year-old former leader was admitted for tests “consistent with his age.” The statement said there is “no cause for alarm.”

Meanwhile, South Africans are expressing concern for the iconic former leader. Worshippers gathered at the Regina Mundi Catholic Church in Soweto Sunday to offer prayers for Mr. Mandela.

He has grown frail and has not made a public appearance in several years. In February, he was briefly hospitalized for abdominal pain.

Mr. Mandela became South Africa's first black president in 1994. Prior to becoming president, he spent 27 years in prison for his fight against apartheid.