Former Nigerian president Muhammadu Buhari - who led his country first as a junta strongman and later as an elected democrat - died Sunday at the age of 82, an aide said.

Buhari governed Nigeria with a strong hand as a military ruler in the 1980s before reinventing himself as a"converted democrat", serving two terms from 2015 to 2023.

"The family of the former president has announced the passing of the former president, Muhammadu Buhari, this afternoon in a clinic in London," Garba Shehu, who served as Buhari's spokesperson during his presidency, said in a post on social media.

Current President Bola Tinubu said in a statement that he had spoken with Buhari's widow and ordered Vice President Kashim Shettima to go to England to accompany Buhari's body back to Nigeria.

The 82-year-old Muslim from Nigeria's far north made history as the first opposition candidate to defeat an incumbent leader at the ballot box in 2015.

His election victory in a country where re-election for the incumbent had been taken for granted was seen as a rare opportunity for Nigeria to change course.

But his time at the helm failed to halt the country’s long-standing issues of graft and insecurity, while economic woes further dogged the oil giant.