“President Jacob Zuma wishes to advise that former president Nelson Mandela was admitted to hospital today, the 25th February 2012,” a statement from the presidency said.
“Madiba has had a long-standing abdominal complaint and doctors feel it needs proper specialist medical attention.”
The health of the increasingly frail anti-apartheid icon, who is affectionately known as Madiba, sparked national fears after he was hospitalised early last year for an acute respiratory infection.
“We wish him a speedy recovery and assure him of the love and good wishes of all South Africans and people throughout the world,” the statement from the presidency said.
“We request that all respect the privacy of Madiba and that of his family during this period.”
The name of the hospital to which he has been admitted was not released.
Mandela returned to his Johannesburg home last month from his rural home village in the Eastern Cape, some 800 kilometres (500 miles) from Johannesburg, where he moved after his respiratory infection scare.
However he is rarely seen in public with his last appearance at the final of the football World Cup hosted by South Africa in July 2010.
Rumours over his health flare up periodically on social networking sites.
In December, a local television station aired archive footage of his January 2011 hospitalisation which spurred a series of tweets mistakenly announcing new ill health concerns.
The presidency had to issue an assurance of his health to quell the rumours, while his Nelson Mandela Foundation, which guards the anti-apartheid struggle icon’s legacy, also denied them.
Mandela was released from 27 years in prison on February 11, 1990, and oversaw South Africa’s path to its first democratic vote in 1994 when he was elected its first black president after decades of white-minority rule.
He won the Nobel Peace Prize in 1993 and served one term before stepping down in 1999.