Updated

South Africa's presidency says Nelson Mandela has spent a night in the hospital after he was admitted for tests.

Presidential spokesman Mac Maharaj said Sunday there were no updates on 94-year-old Mandela's condition since he went to a hospital in Pretoria on Saturday afternoon.

In a statement Saturday, Maharaj said the medical tests for the anti-apartheid leader and former president were scheduled and that doctors have indicated there is no cause for "alarm."

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

Mandela's latest hospitalization 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 realize 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.

Just a few days ago, Graca Machel, the Mozambican wife of Mandela, appeared at a memorial service for Macia east of Johannesburg and issued a rare denunciation of conditions in South Africa, warning of "big trouble" because of the alleged role in his death of police officers who are supposed to protect the public.

"We have all been correctly angered by the rogue elements and criminals who molest women and children and commit other extreme forms of violence," President Jacob Zuma said in a recent speech to traditional leaders.

"The outrage expressed by our people at such recent violent incidents in particular is most welcome as it indicates that South Africans have not lost their sense of right and wrong," he said. Zuma asserted that "general crime" had decreased over the years, but acknowledged that violence against women and children remains high and he encouraged efforts to rebuild the "moral fiber" of South African society.

The former president has become increasingly frail over the years. In January 2011, 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. 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.