Botswana's former president Festus Mogae, who led the diamond-rich nation for a decade and won praise for good governance and the fight against HIV/AIDS, has died at the age of 86, the government said, declaring three days of national mourning.

Mogae served as Botswana's third president from 1998 to 2008, handing power to his vice president, Ian Khama in a smooth transition that highlighted the southern African nation's reputation for political stability.

An economist by training, Mogae was credited with successful management of Botswana's economy. He tackled HIV/AIDS openly at a time when Botswana faced one of the world's highest infection rates, and adopted one of the African continent's most comprehensive programmes against it.

Born in Serowe on August 21, 1939, Mogae studied in Britain before joining Botswana's civil service shortly after independence in 1966. He served as finance minister and vice president before becoming president.

Mogae stepped down after the maximum of two terms allowed by the constitution.