Security stepped up at Mandela hospital South African police on Tuesday tightened security at the Pretoria hospital where ailing anti-apartheid icon Nelson Mandela was spending his fourth day in intensive care battling a lung infection. On Monday, the arrival of his former wife Winnie Madikizela-Mandela and the couple's daughter Zindzi prompted a scuffle between security and photographers camped outside the clinic. Images of Zindzi Mandela's car and of the security