Brazil football legend Pele is in a special care unit, according to the hospital in which he is staying in Sao Paulo.
The 74-year-old was taken to hospital on Monday with an urinary infection.
It was the second time in two weeks that he has been admitted for treatment.
"Edson Arantes do Nascimento (Pele) remains in hospital. To receive the best care he was transferred in order to be monitored in a special care unit," read a statement released by the Albert Einstein hospital in Sao Paulo.
Jose Fornos Rodrigues, the former player's personal aide, said Pele was "completely fine" and the move was primarily to protect his privacy.
"He was uncomfortable with so many people coming. It'll be quieter now," Mr Rodrigues said.
However, Pele, often called the greatest soccer player in history, has suffered a long list of health problems in the past decade, including emergency eye surgery for a detached retina and a hip replacement.
Pele underwent surgery for kidney stones on November 13 before being released two days later.
Media reports in Brazil say it is possible Pele picked up an infection during the operation to remove the kidney stones, and that the current treatment is normally straightforward.
The much-loved star won three World Cups as a player.
He is the only three-time winner of the World Cup.
Pele won his first World Cup in 1958 as a teenager and added two more in 1962 and 1970.
He finished his career playing in the US with the New York Cosmos.
Brazil hosted the World Cup earlier this year, allowing Pele, named "Football Player of the Century" by soccer governing body Fifa and "Athlete of the Century" by the International Olympic Committee, to take centre stage again and make millions of dollars in endorsements.
Pele is easily one of the best recognised faces in sport.
Companies including Swiss watchmaker Hublot SA, Procter & Gamble Co, Volkswagen AG and Emirates airline signed contracts with the former Brazil international in the past two years.
Yesterday, on his official Twitter feed, Pele welcomed Los Angeles Dodger pitcher Clayton Kershaw as the latest brand ambassador for sandwich company Subway.
Before the World Cup, the former footballer crossed continents several times on behalf of his sponsors.
Two years ago, on November 15, 2012, he underwent a hip operation in the same hospital.
Pele, nicknamed O Rei (The King), was born in a humble home in the Brazilian city of Tres Coracoes, and is considered by many as the greatest footballer in history with his exploits for Brazil and a career which saw him score 1,281 goals in 1,363 games.
During his international career, Pele scored 77 goals in 91 games for his country and won his first World Cup aged just 17, scoring twice in the thrilling 1958 final win over hosts Sweden.
(© Independent News Service)