Chad's President Idriss Debby has died while visiting troops on the front lines of a fight against northern rebels, an army spokesman said on Tuesday. Deby's death comes just one day after he was declared the winner of a sixth term in office, marking over 30 years in power.

On Monday, his campaign said he was headed to the northern part of the country to join troops in fighting "terrorists." Rebels based in Libya had attacked a border post on Monday, and advanced hundreds of kilometers south across the desert, towards the capital N'Djamena. Following the clashes, Chad's army said it had killed 300 rebels and quashed the offensive.

Army spokesman Azem Bermendao Agouna announced Deby's death on state television and radio, surrounded by military officers he referred to as the National Council of Transition.

"A call to dialogue and peace is launched to all Chadians in the country and abroad in order to continue to build Chad together," said Agouna. "The National Council of Transition reassures the Chadian people that all measures have been taken to guarantee peace, security and the republican order."

The circumstances of Deby's death could not immediately be independently confirmed due to the remote location of the battlefield.

Deby, 68, began his 30-year rule of the country in 1990, and is one of Africa's longest-serving leaders.

On April 11, Deby won over 79% of the vote. His long rule in the region's harsh political sphere has made him a strong figure in the French-led campaign against jihadist insurgents in the Sahel.

Last August, the National Assembly named Deby the first field marshal in Chad's history, after he led an offensive against jihadists in the west of the country.