Chad's President Idriss Deby has died while visiting troops on the frontline of a fight against northern rebels, the army said on Tuesday, the day after Deby was declared the winner of a presidential election.

His campaign said on Monday he was joining troops on the frontline after rebels based across the northern frontier in Libya advanced hundreds of km (miles) south toward the capital N’Djamena.

His death is a blow to France, which had based its Sahel counter-terrorism operations in the Chadian capital, N’Djamena.