GABORONE, Botswana (AP) — Festus Mogae, Botswana’s former president who made a national priority of the fight against HIV and AIDS during his tenure from 1998 to 2008, has died at the age of 86, the government said Friday. No cause of death was given.

Botswana President Duma Boko said that under Mogae’s leadership, the country earned international respect for principled, sound economic management and a commitment to democracy. He said the country would undergo three days of national mourning in honor of its former head of state.

Botswana, a sparsely populated and arid country in southern Africa, is the biggest producer of diamonds by value and the second biggest by volume behind Russia. Diamonds account for around 80% of Botswana’s exports and a quarter of its gross domestic product, according to the International Monetary Fund.

Mogae is credited with championing the fight against HIV/AIDS in Botswana, which he made a national priority, and launched free access to antiretroviral drugs at public health facilities in 2002 and extending it to noncitizens in 2019.

This led to a significant decease in the prevalence of HIV/AIDS in the country, which at the time had one of the highest infection rates in the world.

Boko said Mogae carried the name of Botswana with dignity across the world and remained a voice of reason, unity and progress throughout his life.

“Today Botswana mourns a distinguished statesman, a patriot whose life was devoted to the service of his country,” said Boko in an address to the nation.

Mogae won the Ibrahim Prize for Achievement in African Leadership — one of the most prestigious honors for African governance — recognizing his democratic leadership and peaceful transfer of power.

Botswana has unearthed all of the world’s largest rough diamonds over the last decade, including a 2,492-carat stone discovered last year that was the second-biggest diamond ever dug out of a mine and the biggest in more than a century.

Mogae, an economist by profession, was the governor of the Bank of Botswana before leading the country.