Chad's civil society groups are calling for a public demonstration, demanding the dissolution of the Transitional Military Council, which is headed by the new leader General Mahamat Idriss Déby.
He was appointed following the shocking death of his father President Idriss Déby, who died this week after battling rebels on the frontline.
"We are calling on the Chadian population all over the country to take to the streets on Tuesday for a public demonstration, and we will stay on the streets if we are not listened to," said one of the civil society group's leaders Max Loalngar.
"We place ourselves under the protection of the African Union and the United Nations and ask that mechanisms be urgently set into motion to ensure the protection of citizens, to take charge of the process of comprehensive and inclusive dialogue to build a consensual transition and to create the conditions that guarantee a lasting political handover," he told a press conference on Saturday.
'No to the monarchization of Chad by France'
France and regional allies have backed the fallen president's son to take power.
But the opposition does not want the former colonial ruler meddling in its affairs.
"We, the Chadian artists members of the platform 'In the name of respect' demand the non-involvement of the French policy of double standards in the management of Chadian affairs," said Chadian artist Djigri Parterre.
"We say no to the monarchization of Chad by France."
The French President Emmanuel Macron attended Idriss Deby Itno's funeral.
France has been a key ally in the fight against deadly insurgencies in the Sahel and has some 5,100 troops stationed in the region.
But Macron also called on the newly-appointed military government to foster "stability, inclusion, dialogue, democratic transition".
A similar message was conveyed personally to Deby's son when he met earlier with Macron and the presidents of Burkina Faso, Mali, Mauritania and Niger, a French presidential aide said.
The African Union meanwhile called on Chad's security forces "to respect the constitutional mandate and order, and to expeditiously embark on a process of restoration of constitutional order and handing over of political power to the civilian authorities."
The body's Peace and Security Council also called for "an all-inclusive national dialogue" and expressed "grave concern" over said the establishment of a military council.
The younger Deby, a 37-year-old four-star general commanding the elite Republican Guard, was named president and head of a military council immediately after his father's death was announced. Parliament and the government were dissolved.
He will wield full powers but has promised "free and democratic" elections after an 18-month transition period that can be extended once.
The move has been branded an "institutional coup" by the opposition.
The International Federation of Human Rights (FIDH), underscoring the "terrible repression" under Deby, on Friday urged the swiftest possible return to civilian rule.
Deby's death was announced the day after he was declared the winner of an April 11 election -- giving him a sixth mandate after three decades at the helm.
The army said the 68-year-old had died on Monday from wounds suffered while leading troops in battle against rebels who had crossed from Libya.
The Front for Change and Concord in Chad (FACT) has vowed to pursue its offensive after a pause for the funeral, with spokesman Kingabe Ogouzeimi de Tapol telling AFP that the rebels were "en route to N'Djamena".