Thousands of people attended the funeral of Chad's President Idriss Deby on Friday, with French President Emmanuel Macron leading tributes to the long-ruling strongman whose death in a battle with rebels has thrown the country into crisis.

Macron said France would not let anyone threaten the stability of its former colony - a reflection of worries that more turmoil will hamper the fight against Islamist militants across the Sahel region.

France also supported a transition to democracy in Chad, Macron said in his speech to mourners.

Deby, a lynchpin in Western security strategy, was killed on Monday in a battle against a rebel army led by dissident army officers who are not linked to jihadists.

The rebels said on Friday their command centre was bombed on Wednesday night in an attempt to kill their own leader.

They have swept south across the vast desert nation from their bases in Libya towards the capital, N'Djamena, but called a temporary ceasefire to allow Deby's funeral to take place.

African presidents and prime ministers joined dignitaries and ordinary citizens in the capital's Place de la Nation for the funeral ceremony.

Deby's coffin, draped in a national flag, was carried on a military truck flanked by a motorcycle escort. Weeping swelled from the crowd and a 21-gun salute boomed across the city.

Macron was seated for the ceremony next to Deby's son Mahamat Idriss Deby, who along with a military council has taken charge in Chad.

"France will not let anybody put into question or threaten today or tomorrow Chad's stability and integrity," Macron said in his speech.

"France will also be there to keep alive without waiting the promise of a peaceful Chad creating a place for all of its children and components," he said, calling the late president a friend and courageous soldier who had given his life to his country.

Human rights groups have accused France and other Western powers of turning a blind eye to government repression during Deby's 30-year rule because of his co-operation on security matters.

Nonetheless, many Chadians were deeply upset by Deby's death.

"He protected us for so long that today we have come to wish him eternal rest. A deserved rest," said N'Djamena resident Hassan Adoum.

Before the ceremony, Macron and regional leaders met with Mahamat Idriss Deby and members of the military transition council.

The 37-year-old Deby, who holds the rank of general, has dissolved parliament, taken over as president and armed forces commander, and promised to hold an election in 18 months time.

A French presidency source said France and the G5 Sahel nations had offered support for a civilian-military transition in Chad for the good of regional stability. The G5 are Burkina Faso, Chad, Mali, Mauritania, and Niger - all beset by Islamist militant threats.

(With input from agencies)