Nigeria's former President Muhammadu Buhari died in London on Sunday following a "prolonged illness," a presidential spokesperson said.

"President Buhari died today in London at about 4:30 p.m. (1530 GMT)," President Bola Tinubu's spokesperson wrote in a post on X.

He did not disclose the nature of the 82-year-old's illness.

Buhari had been in the UK for the past three months.

Army ruler then democratic leader

Buhari first led Africa's most populous nation as a military ruler after a coup in the 1980s.

He later rebranded himself as a "converted democrat" and then defeated incumbent President Goodluck Jonathan in 2015 in what was judged to be Nigeria's fairest election to date.

He remained in power until 2023.

Buhari's health kept under wraps

Tinubu ordered flags to fly at half-staff in honour of Buhari, whose tenure was dogged by health rumours.

Buhari's government faced accusations of a lack of transparency over his illness, especially as he sometimes took long absences.

However, Buhari's health was still kept from the public, although he admitted that during one of the trips he had "never been so ill" and that he had received several blood transfusions.

Initial rule brief, but Buhari made comeback

Buhari seized power in 1983 as a military ruler, promising to revitalize a mismanaged country.

Taking a tough line on corruption, he also questioned Nigeria's bailout conditions sought by the International Monetary Fund.

But his first stint was short-lived. He was removed after only 18 months by another military officer, Ibrahim Babangida, and spent much of the following 30 years in fringe political parties and trying to run for president.

After his 2015 election win, Buhari took six months to name his cabinet. During that time, the oil-dependent economy was hobbled by low crude prices, prompting people to call him "Baba Go Slow."

He won a second victory in 2019, despite his first term being blighted by Nigeria's first recession in a generation, militant attacks on oilfields, and repeated hospital stays.

Security worsened under Buhari

Many hoped Buhari, a retired major general, would crack down on armed groups, just as he had as the country's military head of state.

In 2009, the likes of Boko Haram began an Islamist insurgency, initially confined to the northeast, but which later spread to other regions, leaving swathes of Nigeria outside the control of its stretched security forces.

Boko Haram and its splinter faction, the Islamic State West Africa Province (ISWAP), later turned to suicide bombings, kidnappings, and attacks on civilians and military targets.

During 16 years of violence, more than 36,000 people have been killed and another 2 million displaced, according to the United Nations.

Edited by: Jenipher Camino Gonzalez