Anglican Archbishop Emeritus Desmond Tutu, who is aged 83, has re-entered the hospital, a week after he was discharged, his foundation has said.
"He was discharged from hospital last Tuesday, and re-admitted this afternoon after expressing renewed discomfort," the Desmond and Leah Tutu Legacy Foundation said in a statement on July 28.
"His doctors considered it prudent for him to return to hospital for observation.
"He'll have a few days of bed-rest while his medical dream team brings the situation under control and determines the next course of action, if any.
"He will stay in hospital until the weekend, at least," his daughter Reverend Canon Mpho Tutu said.
She said he hospital admission was unrelated to his prostate cancer treatment, noting that his oncologist had said his prostate-specific antigen level was "pleasingly low."
The previous admission of the 1984 Nobel Peace Prize laureate was to treat an infection.
Tutu attended a ceremony July 4 in the Holy Cross Anglican Church in Soweto where he and his wife held a marriage vow renewal ceremony in the area where they used to live.
The Associated Press reported Tutu danced stiffly as choristers sang and was frequently on his feet, thanking the congregants at the end of the three-hour event. At other times, he sat with his eyes closed, the news agency said.
Tutu is regarded as one of South Africa's most outspoken leaders, and while he was the scourge of those heading the apartheid regime, he has also strongly criticized current President Jacob Zuma for corruption on a number of occasions
He chaired the Truth and Reconciliation Commission aimed at addressing the wrongs of apartheid while serving as a vehicle of forgiveness.
Tutu is the former Archbishop of Cape Town and former Southern Africa Anglican leader.