South African President Jacob Zuma says Nelson Mandela is "very serious but stabilised" in hospital and that "all are praying" for his recovery.Mr Zuma said the doctors were doing a "very good job", adding that the former president was a "good fighter".The 94-year-old is spending his fourth day in a Pretoria hospital suffering from a recurrent lung infection.Relatives, including his ex-wife Winnie Madikizela-Mandela, visited the ailing former leader on Monday.The former president has been in intensive care since he was admitted to the hospital on Saturday for the third time this year.In December, Mr Mandela spent 18 days undergoing treatment for a lung infection and gallstones.'Good fighter'Referring to Mr Mandela as "the father of democracy in South Africa", Mr Zuma said: "We need him to be with us and I'm sure all the messages that have been pouring in to wish him a speedy recovery are highly welcome."And I'm sure, knowing him as I do, he is a good fighter. He will be with us very soon."Mr Zuma was speaking in a televised interview broadcast on Tuesday evening, having been given a "thorough briefing" on Monday by Mr Mandela's doctors.Mr Zuma said: "I was very confident that they know what they are doing and they are doing a very good job, whilst he is very serious but he is stabilised and we are all praying for him, really, to recuperate quickly."We need him to go with us," added the ANC leader.Before being admitted to hospital, Mr Mandela had been ill for some days at his Johannesburg home, with a recurrence of his long-standing lung problems, said a statement from the president's office earlier on Tuesday.He was taken to hospital when his condition worsened at 01:30 on Saturday (23:30 GMT Friday).Widely referred to by his clan name Madiba, Nelson Mandela served as president from 1994 to 1999.He was previously imprisoned for 27 years, and is believed to have suffered damage to his lungs while working in a prison quarry.He contracted tuberculosis in the 1980s while being held in jail on the windswept Robben Island.He retired from public life in 2004 and has been rarely seen at official events since.