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.
Mr Déby, 68, spent three decades in power and was one of Africa's longest-serving leaders.
A military council led by Mr 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 on Tuesday.