 Story highlights Mandela remains "under treatment and observation," President Jacob Zuma says 
 
 The anti-apartheid icon also was hospitalized earlier this month 
 
 At the time, officials said it was only for a routine checkup 
 
 Mandela, 94, has been treated for a lung infection before 
 
 Former South African President Nelson Mandela is "responding positively" to treatment after he was readmitted to a hospital overnight for a recurring lung infection. "He remains under treatment and observation in hospital," Zuma said Thursday. “The Presidency appeals once again for understanding and privacy in order to allow space to the doctors to do their work.” 
 
 Mandela, 94, was taken to a hospital just before midnight local time (6 p.m. This was the longest time he had been hospitalized since being released from captivity as a political prisoner in 1990. More than two weeks ago, he was taken to a hospital for what officials described as a routine checkup. Launch slideshow 
 
 'Be strong' 
 
 Jackson Mthembu, a spokesman for the African National Congress, said in a statement that the party once led by Mandela “calls on all South Africans and the world to keep Nelson Mandela in their prayers.” 
 
 “We are confident that the treatment will be successful as he is in professional and competent hands,” he said. Mandela was president of South Africa from 1994 to 1999, the first president of the country to be elected following the fall of the apartheid system. "He is as strong physically as he's been in character and in leadership over so many decades, and hopefully he will ... come out of this latest challenge," Obama told reporters at the White House. Hide Caption 30 of 30 
 
 JUST WATCHED 2012: Nelson Mandela back home Replay More Videos ... MUST WATCH 2012: Nelson Mandela back home 02:42 
 
 "Doctors are attending to him, ensuring that he has the best possible expert medical treatment and comfort," Zuma's office said in an earlier statement Thursday. In a statement, the current South African President Jacob Zuma said, “We appeal to the people of South Africa and the world to pray for our beloved Madiba [a nickname for Mandela] and his family and to keep them in their thoughts.” 
 
 “We have full confidence in the medical team and know that they will do everything possible to ensure recovery,” he added. Josh Earnest, White House deputy press secretary, said President Barack Obama is being updated on Mandela's health. “During these trying times we wish President Mandela well and for his family to be strong," he added. He underwent treatment for a lung infection and had surgery to remove gallstones over the Christmas holiday in 2012, one of his longest hospital stays since his release from prison in 1990.
– Weeks after returning home from the hospital, Nelson Mandela was admitted again last night for a lung infection. South African president Jacob Zuma is calling on the world to offer its support to the 94-year-old icon, NBC News reports: "We appeal to the people of South Africa and the world to pray for our beloved Madiba and his family and to keep them in their thoughts," Zuma said. "We have full confidence in the medical team and know that they will do everything possible to ensure recovery." Mandela, who CNN notes was conscious when admitted last night, was hospitalized for weeks in December with a lung infection and has battled respiratory problems for years.