Chadian President Idriss Deby Itno, who ruled the central African nation for more than three decades, died of wounds suffered on the battlefield during a fight against rebels, the military has announced.
The announcement on national television and radio came just hours after electoral officials had declared Mr Deby, 68, the winner of the April 11 presidential election, paving the way for him to stay in power for six more years.
An 18-month transitional council will be led by Mr Deby’s 37-year-old son Mahamat Idriss Deby Itno, the military said, while also imposing a nightly curfew of 6pm.
“In the face of this worrying situation, the people of Chad must show their attachment to peace, to stability, and to national cohesion,” General Azem Bermandoa Agouma said.
The circumstances of Mr Deby’s death could not immediately be independently confirmed due to the remote location of the fighting.
The military said Mr Deby had taken “the heroic lead in combat operations against terrorists who had come from Libya”.
After being wounded in battle, he was then taken to the capital N’Djamena, the general announced.
However, some foreign observers questioned how a head of state could have been killed, saying it cast doubt on his protective guard.
The Chadian military had only acknowledged five deaths in weekend fighting in which it said it had killed 300 rebels.
“We still don’t have the whole story,” Laith Alkhouri, a global intelligence adviser, told the Associated Press.
“It raises concerns regarding the security forces’ assessment of the clashes and their intelligence regarding the severity of the situation.”
Other analysts pointed to Mr Deby’s long history of visiting the battlefield as a former army commander-in-chief himself.
“There’s no evidence to suggest this was a coup committed by his troops. Anyone who follows Deby knows he used to say ‘to lead troops you have to smell the gunpowder’,” tweeted Cameron Hudson, of the Atlantic Council’s Africa Centre.
Mr Deby first came to power in 1990 when his rebel forces overthrew then-president Hissene Habre, who was later convicted of human rights abuses at an international tribunal in Senegal.
Over the years, Mr Deby had survived numerous armed rebellions and managed to stay in power until this latest insurgency led by a group calling itself the Front for Change and Concord in Chad.
The rebels are believed to have armed and trained in neighbouring Libya before crossing into northern Chad on April 11.
Their arrival came on the same day that Chad’s president sought a sixth term on election day, which several top opposition candidates boycotted.
Mr Deby was a major French ally in the fight against Islamic extremism in Africa, hosting the base for the French military’s Operation Barkhane and supplying critical troops to the peacekeeping effort in northern Mali.
Mr Deby’s son, Mahamat, has served as a top commander for Chadian forces taking part in that effort.