Details of his death are still sketchy but the army authorities said he died from injuries sustained on the war front.
The Chadian army is currently combating rebel forces who have launched an assault on the capital, N’Djamena.
Deby, 68, “has just breathed his last defending the sovereign nation on the battlefield” over the weekend, army spokesman, General Azem Bermandoa Agouna, said in a statement read out on state television.
General Mahamat Kaka, the son of the deceased Chadian leader, has been named interim head of the state, the army spokesman said.
The news came a day after Deby, who came to power in a rebellion in 1990, won a sixth term, as per provisional results released on Monday. Deby took 79.3 per cent of the vote in the April 11 presidential election, the results showed.
Deby postponed his victory speech to supporters and instead went to visit Chadian soldiers battling rebels, according to his campaign manager.
The rebel group, Front for Change and Concord in Chad (FACT), which is based across the northern frontier with Libya, attacked a border post on election day and then advanced hundreds of kilometres south.
But it suffered a setback over the weekend.
Chad’s military spokesman Agouna, told the Reuters news agency that army troops killed more than 300 fighters and captured 150 on Saturday in Kanem province, around 300 kilometres from the capital Ndjamena.
