Chad's President Idriss Deby, who ruled his country for more than 30 years and was an important Western ally in the fight against Islamist militants in Africa, has been killed in a battle against rebels in the north. His son, Mahamat Idriss Deby Itmo, was named interim president by a transitional council of military officers, army spokesman Azem Bermendao Agouna said on state television. Deby, 68, took power in a rebellion in 1990 and was one of Africa's longest-ruling leaders, surviving numerous coup attempts and rebellions. He was killed just after he was declared winner of a presidential election that would have given him a sixth term in office. Most of the opposition boycotted the vote. How he died isn't yet clear, but Bermendao said Deby - who often joined soldiers on the battlefront in his military fatigues – took charge against advancing "terrorists from Libya" on Monday.