Chad’s President Idriss Déby has died of his injuries following clashes with rebels in the north of the country at the weekend, the army has said.
The announcement came a day after provisional election results projected he would win a sixth term in office.
The government and parliament have been dissolved. A curfew has also been imposed and the borders have been shut.
Déby, 68, spent more than three decades in power and was one of Africa’s longest-serving leaders.
An army officer by training, he came to power in 1990 through an armed uprising. He was a long-time ally of France and other Western powers in the battle against jihadist groups in the Sahel region of Africa.
Déby “breathed his last defending the sovereign nation on the battlefield”, an army general said on state TV on Tuesday.
He had gone to the front line, several hundred kilometres north of the capital, N’Djamena, at the weekend to visit troops battling rebels belonging to a group calling itself Fact (the Front for Change and Concord in Chad).
A state funeral is due to take place on Friday.
A military council led by Déby’s son, a 37-year-old four star general, will govern for the next 18 months.
Mahamat Idriss Déby Itno will lead the council, but “free and democratic” elections will be held once the transition period is over, the army said in its statement.
He later issued a statement naming the 14 other generals who will make up the new governing body.
Ahead of the election on 11 April, Déby campaigned on a platform of bringing peace and security to the region. Provisional results showed he had 80% of the vote.
But there had been growing unhappiness over his government’s management of Chad’s oil resources.
Idriss Déby was known as that rare thing – a true warrior president. The former rebel and trained pilot was the opposite of an armchair general.
For 30 years, he clung to power in Chad – a vast nation that straddles the Sahara and is surrounded by some of the continent’s most protracted conflicts.
And Déby had a hand in every one of them – from Darfur to Libya, Mali, Nigeria and the Central African Republic. His troops were among the most battle-hardened on the planet.
Domestically, he had become an increasingly autocratic figure. His latest election victory saw him claim nearly 80% of the vote.
It is unclear if the poor, feuding, brittle state he leaves behind can manage a smooth transition.
And there are wider concerns too. For years, President Déby was the West’s indispensable ally in the war against Islamist militants – in Mali, Niger and beyond.
His death leaves a vacuum that many may now fight to fill.