Botswana's former president Festus Mogae, who led the southern African country for a decade from 1998, winning praise for the fight against HIV/AIDS, has died at the age of 86, the presidency said on Friday.

An economist who studied in Britain, he oversaw strong economic growth during his two five-year terms in office.

"As a nation, we grieve the loss of a remarkable leader and servant of the people whose commitment to Botswana remained unwavering throughout his life," current President Duma Boko said.

The government declared three days of national mourning, with flags to be flown at half-mast.

Mogae came to power as the country's third president after Ketumile Masire stepped down, having previously served as his vice-president.

Winner Ibrahim Prize

He was succeeded by Ian Khama in 2008, a former military chief and son of Botswana's first president.

Mogae is credited with tackling HIV/AIDS openly at a time when Botswana faced one of the world's highest infection rates.

In 2008, he won the prestigious Ibrahim Prize for his leadership in sustaining the country's stability and prosperity during the crisis.

After leaving office, he chaired the Joint Monitoring and Evaluation Commission, playing a key role in overseeing South Sudan's peace process.