N'DJAMENA, Chad (AP) — Chadian President Idriss Deby Itno, who ruled the central African nation for more than three decades, was killed Tuesday on the battlefield in a fight against rebels, the military announced on national television and radio.

An 18-month transitional council will be led by Deby’s 37-year-old son, Mahamat Idriss Deby Itno, the military said, also imposing a nightly curfew of 6 p.m.

The stunning announcement came just hours after electoral officials had declared Deby the winner of the April 11 presidential election, paving the way for him to stay in power for six more years.

The circumstances of Deby's death could not immediately be independently confirmed due to the remote location of the battlefield. It was not known why the president would have visited the frontlines in northern Chad or participated in ongoing clashes with the rebels who opposed his rule.

Deby, a former army commander-in-chief, 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 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 neighboring 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.

Deby was a major French ally in the fight against Islamic extremism in Africa, hosting the base for the French military Operation Barkhane and supplying critical troops to the peacekeeping effort in northern Mali.

Deby's son, Mahamat, has served as a top commander for Chadian forces taking part in that effort.