Former president Nelson Mandela and worldwide peace icon, is in hospital for the second night in a row in South Africa, after going in for a recurring lung infection. Doctors say is in "serious but stable".

The Associated Press notes that the 94-year-old anti-apartheid leader has been in and out of hospital after doctors diagnosed him with pneumonia and drained fluid from his lung area.

Mandela, the man who led South Africa's fight for freedom against the racist apartheid regime, has been particularly vulnerable to respiratory problems since contracting tuberculosis during his 27-year imprisonment under apartheid. He contracted tuberculosis in the 1980s while being held in jail on the windswept Robben Island.

This is his fourth hospital stay in seven months. Mandela's wife, Graca Machel, cancelled a scheduled appearance in London to remain at her husband's bedside.

Meanwhile, South African President Jacob Zuma has continued to hold engagements away from the capital.

"Our thoughts and prayers are with him, his family and the people of South Africa as he recovers," US National Security Council spokeswoman Caitlin Hayden said.

President Barack Obama, who has often called Mandela an inspirational figure, was concluding two days of informal talks with his Chinese counterpart Xi Jinping in California.