South African Archbishop emeritus Desmond Tutu was hospitalised Tuesday with a persistent infection just a week after being discharged following treatment for the same ailment, his foundation said.

"Archbishop Emeritus Desmond Tutu has been re-admitted to a hospital in Cape Town... He was discharged from hospital last Tuesday, and re-admitted this afternoon after expressing renewed discomfort. His doctors considered it prudent for him to return to hospital for observation," a statement by the Desmond and Leah Tutu Legacy Foundation said.

Tutu was first hospitalised for the infection on July 14.

The 83-year-old Nobel peace laureate also continues battling prostate cancer he has lived with for 15 years, but his foundation said the current infection was unrelated.

"(Tutu's) daughter, the Reverend Canon Mpho Tutu, said the hospitalization was unrelated to his cancer treatment. His oncologist confirms that his PSA (prostrate-specific antigen) level is pleasingly low," it said.

The foundation said the veteran rights campaigner would undergo bed rest while his doctors determine further treatment, and remain in the hospital at least through the weekend.

Tutu survived an illness believed to be polio as a baby, and battled tuberculosis as a teenager. He has been in and out of hospital for minor complaints since 2011.

Under apartheid, Tutu campaigned against white minority rule during the years that Nelson Mandela was imprisoned, and was awarded the 1984 Nobel Peace Prize for his work.

Officially retired, he is still outspoken on the world's injustices, and is widely viewed as South Africa's moral compass.