JOHANNESBURG, South Africa (AP) — Nelson Mandela, the former South African president and anti-apartheid leader, was yesterday admitted to hospital for a scheduled medical check-up, and doctors say there is no cause for "alarm", the president's office said.

Officials have used similarly soothing language to explain previous hospital stays for 94-year-old Mandela, but in those cases he later turned out to have more serious conditions. The intense privacy surrounding the health of Mandela reflects in part the official reverence for a man who is seen as one of the great, unifying figures of the 20th century for helping to avert race-driven chaos in South Africa's tense transition from apartheid to democracy.

Presidential spokesman Mac Maharaj said Mandela went for tests "to manage existing conditions in line with his age" at a hospital in Pretoria, the capital.

"Doctors are conducting tests and have thus far indicated that there is no reason for any alarm," Maharaj said in a statement. He appealed for the public to respect the privacy of Mandela and his family.

The former president was hospitalised for nearly three weeks in December, before going home on December 26. At that time, he was treated for a lung infection and had a surgical procedure to remove gallstones.

Mandela has become increasingly frail over the years. In January 2011, he 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. He also had surgery for an enlarged prostate gland in 1985.

Under South Africa's white-minority apartheid regime, Mandela spent 27 years in prison, where he contracted tuberculosis, before being released in 1990.

He later became the nation's first democratically elected president in 1994 under the banner of the African National Congress. He served one five-year term before retiring.

The Nobel laureate last made a public appearance on a major stage when South Africa hosted the 2010 World Cup soccer tournament.

Mandela's latest hospitalisation comes at a time when South Africa is enduring a series of setbacks that serve as a reminder of how it has fallen short of the kind of harmonious society that he envisioned, but could not realise during his five years as the country's first black president.

The nation of 50 million has long struggled with poverty and inequality since it emerged from white minority rule. But crisis hit in August, when police shot and killed 34 striking miners at the Marikana platinum mine in a spasm of violence that drew comparisons among some South Africans with Sharpeville in 1960, Soweto in 1976 and other mass killings by agents of the apartheid state.

Then came February, when the gang-rape and killing of 17-year-old Anene Booysen highlighted the scourge of violence against women in South Africa; the arrest of Oscar Pistorius, South Africa's double-amputee athlete who inspired millions at the London Olympics, on charges of murdering his girlfriend; and the killing of Mado Macia, a Mozambican taxi driver who was found dead in a South African police cell after he was dragged from a police vehicle in view of onlookers who filmed the shocking incident.