Soldiers have been posted outside 1 Military Hospital to screen vehicles entering the building, where Nelson Mandela is being treated
All vehicles entering at the hospital's are stopped and inspected by Military police before allowing them onto the premises.
Vehicles belonging to news crews, including an outside broadcast vehicle, were turned back at the entrance.
Several journalists milled outside, metres away from the security checkpoint.
On Monday, Defence Minister Nosiviwe Mapisa-Nqakula said Mandela was
"doing very, very well" while undergoing unspecified medical tests at
the military hospital.
She offered the first government confirmation that Mandela, 94, was
at the hospital. He has received military medical care since 2011.
The office of President Jacob Zuma also confirmed on Monday that Mandela was fine, but did not offer further details.
President Zuma visited Mandela on Sunday morning and found him to be "comfortable and in good care".
In February, Mandela spent a night in a hospital for a minor
diagnostic surgery to determine the cause of an abdominal complaint.
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.
Mandela has had other health problems. He contracted tuberculosis
during his years in prison and had surgery for an enlarged prostate
gland in 1985.
In 2001, Mandela underwent seven weeks of radiation therapy for prostate cancer, ultimately beating the disease.