As Chad prepares for the funeral of the former president, Idriss Déby, on Friday, opposition parties in the country have denounced the military takeover, calling it a coup d’etat, and rebel forces are threatening to march on the capital N’Djamena.

Idriss Déby’s son, General Mahamat Idriss Déby, formally took over control as interim president and commander of the armed forces on Wednesday.

Déby said in his first public address that the army wanted to return power to civilian rule and free and democratic elections would be held 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 military also announced it had re-opened Chad’s borders, which were closed after Idriss Déby’s death.

But rebels from the Libyan-based Front for Change and Concord in Chad (FACT), a group formed by dissident army officers, rejected the military’s plan.

“The forces of national resistance are more than ever determined to deliver the Chadian people from this abominable dictatorship,” they said in a statement.

Opposition party leaders condemned what they called “the institutional coup d’etat conducted by the generals”.

Civil society organisations also called for a return to civilian rule and a coalition of armed groups demanded an inclusive national dialogue. Labour unions called for a workers’ strike.

Western allies said they were concerned that the death of Idriss Déby would negatively affect counter-terrorism operations in the Sahel and Lake Chad regions.

Idriss Déby was regarded by many as championing the fight against members of the Jamā’at Ahl as-Sunnah lid-Da’way Wa’l-Jihād (JAS), also known as Boko Haram, and the Islamic State in West Africa Province (ISWAP), as well as insurgents from other militant groups.

Abubakar Mohammed Kareto, a public affairs analyst in Maiduguri, also expressed concern for the region, saying Idriss Déby was “the only African leader who was known for fighting against terror groups in the Sahel region”.

He said the need to fight against insurgent groups could not be overemphasised.

“It is hoped that the interim president General Mahamat Idriss Déby will take up the fight against those who are trying to destabilise the region,” he said.

“I know that the insurgents will be happy about the news of Idriss Déby’s death and will think that they can carry out their operations without any fear or hindrance. They shouldn’t start jubilating yet because they don’t know what plans Mahamat has against them. It is too early for them to celebrate the death of the lion of Africa.

“Mahamat can perform better than his late father if the countries across the Sahel and Lake Chad regions give him maximum support and cooperation in the fight against insurgents across the two regions,” Kareto said.

Residents in Maiduguri were divided in their opinions of Idriss Déby.

Muhammed Muhammed Garga described him as an “icon who protected his country for decades”.

But resident Musa Gambo said “one man’s hero is another man’s villain”.

“Idriss Déby was not a saint. He come to power through a bloody coup that lasted for nine months before toppled his former boss causing one of the highest humanitarian crises in the region.”

Referring to Idriss Déby’s son taking power, Gambo said political offices were not meant to be “inherited”. He said he feared “civil war” in Chad.