Nelson Mandela hospitalised, in serious condition

"During the past few days former president Nelson Mandela has had a recurrence of lung infection," President Jacob Zuma's office said in a statement.

"This morning at about 1:30am (0930 AEST) his condition deteriorated and he was transferred to a Pretoria hospital. He remains in a serious but stable condition," it said.

It marks the second hospitalisation in as many months for the frail anti-apartheid hero, who will turn 95 in July. On April 6 he was released after being treated for pneumonia during a 10-day stay.

The Nobel Peace Prize winner has stayed in hospital four times in just over half a year, mostly over problems with his chest.

In December 2012, he was hospitalised for 18 days for a lung infection and for gallstones surgery, his longest stay in hospital since he walked free from 27 years in jail in 1990.

In March he was admitted for a day for a scheduled check-up and during his 10-day stay weeks later, doctors drained a build-up of fluid, known as a pleural effusion or "water on the lungs", that had developed in his chest.

Mandela has not been seen in public since the World Cup final in 2010, where he appeared on the pitch before kick-off.

Following his April hospital stay, the release of television footage showing a frail and distant Mandela being visited at home by ANC leaders sparked outrage and accusations that the party was exploiting Mandela.

The images aired by state broadcaster SABC -- which were the first public footage of the Nobel peace laureate in almost nine months -- showed an unsmiling, distant Mandela seated upright on a couch, his legs covered in a blanket.