Former South African president Nelson Mandela has been admitted to hospital for routine tests, says the South African government.

The government says there is no reason to be alarmed about the well-being of the 94-year-old national hero.

A message on the website of President Jacob Zuma said this is a "scheduled medical check-up to manage existing conditions in line with [Nelson Mandela's] age."

Presidential spokesman Mac Maharaj said in a statement that Mandela went to a hospital in Pretoria, the capital, on Saturday afternoon.

In the past two years, he has been admitted to hospital on three times. In January 2011, he was treated for a chest infection.

Mandela spent most of last December in hospital for treatment of a lung infection. He also had gallstones removed.

He was expected to receive further treatment at home after being released in late December.

When Mandela was released, President Jacob Zuma declared that Mandela looked "much better" and that doctors were pleased with his progress.

In 2001, Mandela underwent radiation therapy for prostate cancer.

With files from the Associated Press