The clerics, sporting flowing purple robes and white collars and representing a variety of denominations, stood hand-in-hand to say prayers for Mandela, who is said to be improving but still in a serious condition.
“Thank you (God) for the speedy recovery of Dr Nelson Mandela,” said Bishop Abraham Sibiya of the Christ Centred Church Episcopal Soshanguve, to chants of “amen”.
After a visit to the hospital late Thursday, President Jacob Zuma said the health of the country’s first black president “continues to improve but his condition remains serious.”
The hospital is under lockdown and entry is restricted to Mandela’s close family and those cleared to have business inside the hospital.
Sibiya told AFP that church leaders had come out in response to Zuma’s call to pray for the 94-year-old hero of the struggle against white-minority rule.
Zuma’s spokesman Mac Maharaj said he had no update on Mandela’s condition when contacted by AFP early Friday.
Mandela was admitted to hospital in the capital Pretoria in the early hours of Saturday for a pulmonary condition that has plagued him for years.
It is his fourth hospital stay since December, leading to a growing acceptance that the much-loved father of the “Rainbow Nation” may be nearing the end of his life.
Despite the more positive assessment of Mandela’s condition, concerns continue to grow and Zuma has asked the nation to pray for him.
“So we came to pray that God will heal former president Mandela and also we came to pray for the family that God will strengthen them at this difficult time and give them strength to face each and every day they go through,” Sibiya told AFP.
Members of Mandela’s family, known for frequent internal feuding, have been visiting him regularly in a public display of unity.
On Friday morning his daughter Zenani, who is South Africa’s ambassador to Argentina, visited him, as did some grandchildren and great grandchildren.
Mandela has a long history of lung problems since being diagnosed with early-stage tuberculosis in 1988 during his 27 years in prison at the hands of the apartheid regime.
Experts say that infection makes him vulnerable to recurrent lung infections.