- Mahamat Idriss Deby has taken over as president and armed forces commander in Chad.
- Chad's leader Idriss Deby was killed on Monday in a battle against fighters a rebel group.
- Mahamat said the army wanted to return power to a civilian government and hold democratic elections.
The son of Chad's slain leader Idriss Deby took over as president and armed forces commander on Wednesday as rebel forces threatened to march on the capital, deepening the turmoil in a country vital to international efforts to combat Islamist militants in Africa.
The political opposition also denounced the military's takeover of control, calling the move a coup d'etat and rejecting its plan for a transition. Labour unions called for a workers' strike.
Deby, 68, was killed on Monday on the frontline in a battle against fighters of the Libyan-based Front for Change and Concord in Chad (FACT), a rebel group formed by dissident army officers.
His death shocked the nation and raised concerns among Western allies, notably France and the United States, who had counted on him as an ally in their fight against Islamist groups including Islamic State and Boko Haram.
Deby had been in power since 1990 and had just been declared winner of a presidential election that would have given him a sixth term in office. His son, General Mahamat Idriss Deby, was named interim president by a transitional council of military officers.
General Deby, 37, moved to consolidate his position on Wednesday, with the council issuing a new charter in place of the country's constitution granting him the functions of president and also naming him as head of the armed forces.
In his first public comments since taking power, Deby said the army wanted to return power to a civilian government and hold free and democratic elections in 18 months.
"The military council has no ambition to govern the country alone," he said in a speech to political party representatives, posted on the presidency website.
"The Transitional Military Council will work to consolidate democracy, assure peace and stability, guarantee security and the integrity of the national territory."
The military also announced it had re-opened Chad's borders, which were closed after Deby's death.
The FACT rebels rejected the military's plan and said they would press on with their offensive.
"Chad is not a monarchy. There can be no dynastic devolution of power in our country," FACT said in a statement.
OVER THE BORDER
A spokesman for FACT - which is not linked to jihadists - said its forces were now in Kanem region about 200-300 km north of N'Djamena and their aim was to bring democracy to Chad after years of authoritarian rule by Deby.
The fighters poured over the vast country's northern border last weekend.
"We don't want to seize power to hold power. Our objective is for democratic transitions to be a reality," the spokesman said. He said the group was preparing to march on N'Djamena to "free the people from a system that is undemocratic".
FACT claimed responsibility for the injuries that killed Deby on Monday. An ex-army officer who often joined soldiers on the battlefront, Deby was visiting troops who had held up the rebel advance in intense fighting over the weekend.
He was wounded by gunfire in the village of Mele near the town of Nokou, more than 300 km north of N'Djamena, and evacuated to the capital where he later died, the FACT spokesman said. The presidency has not commented on the exact circumstances of his death.
Opposition politicians, many of whom boycotted the election, also called for a return to civilian rule.
In a joint statement, about a dozen party leaders condemned what they called "the institutional coup d'etat conducted by the generals" and called for a civilian transition.
"We do not see ourselves in this military transition. Our position is a return to constitutional order," Dinamou Daram of the Socialist Party Without Borders told Reuters.
The main labour organisation, the Union of Syndicates of Chad, also rejected the military takeover and called for a strike.
Deby had won friends abroad by sending his well-trained army to fight jihadists including Boko Haram in the Lake Chad Basin and groups linked to al Qaeda and Islamic State in the Sahel.
His main ally, France, has about 5 100 troops based across the region as part of international efforts to fight the militants, including its main base in N'Djamena. The United States also has military personnel there.
Paris said it had lost a courageous friend and an important ally. President Emmanuel Macron will go to Deby's funeral.
Regional powerhouse Nigeria's foreign minister said it was willing to help facilitate dialogue, but that while an early return to democratic rule was the ultimate goal, the immediate objective was the stabilisation of Chad and the region.
Human Rights Watch criticised the West's relationship with Deby, saying that for years it had propped up Deby's government while turning a blind eye to his repression. In a statement, it warned of the "potentially explosive consequences" of Deby's death for Chad and the region.
In N'Djamena, where authorities imposed a nightly curfew after Deby's death, schools and some businesses were open on Wednesday but many people stayed home and streets were quiet.
A 14-day period of national mourning is being observed.
"We must make sure that this military council does not take over power," said Djimadoum Ngarteri, a teacher, calling for all sides to lay down weapons. "We Chadians are fed up. We do not need people who take power with weapons."