The statement issued by President Jacob Zuma's spokesman said that Mandela was doing well and was receiving medical care "which is consistent for his age." The statement offered no other details.
Mandela, who spent 27 years in prison for fighting racist white rule, became South Africa's first black president in 1994 and served one five-year term. He later retired from public life to live in his village of Qunu, and last made a public appearance when his country hosted the 2010 World Cup soccer tournament.
"We wish Madiba all the best," Zuma said in the statement, using Mandela's clan name. "The medical team is assured of our support as they look after and ensure the comfort of our beloved founding president of a free and democratic South Africa."
While the government sought to reassure South Africans about Mandela's health, he remains viewed as a father figure to many in this nation of 50 million people. Each hospital trip raises the same worries about the increasingly frail former leader of the African National Congress - that the man who helped bring the nation together is slowly fading away.
In February, Mandela spent a night in a hospital for a minor diagnostic surgery to determine the cause of an abdominal complaint. In January 2011, however, Mandela was admitted to a Johannesburg hospital for what officials initially described as tests but what turned out to be an acute respiratory infection. He was discharged days later.
Mandela contracted tuberculosis during his years in prison. He also had surgery for an enlarged prostate gland in 1985.
While Zuma's statement offered no further details about who would provide medical attention for Mandela, the nation's military has taken over caring for the aging leader since the 2011 respiratory infection. At 1 Military Hospital in Pretoria on Saturday night, the facility that previously cared for Mandela in February, everything appeared calm, without any additional security present.
Mac Maharaj, a presidential spokesman, declined to say whether Mandela had been flown by the military from Qunu to Pretoria. He also declined to say what the tests were for.
"It's quite normal at his age to be going through those tests," Maharaj told The Associated Press.
Mandela's hospitalization comes just days after the crash of a military aircraft flying on an unknown mission near Mandela's rural home in which all 11 onboard were killed.
The plane was flying to a military air base in Mthatha, which is about 30 kilometers (17 miles) north of Qunu. Military officials declined to say whether those on board had any part in caring for Mandela.
Associated Press writers Thomas Phakane in Pretoria, South Africa, and Andrew Meldrum in Johannesburg contributed to this report.