A deadly fire erupted at a huge military ammunition depot in Chad's capital N'Djamena, sending powerful explosions into the night sky and shaking buildings miles from the blast.

The explosions from the late Tuesday blaze turned the sky red and could be heard miles away as ordnance fired off in the flames at regular intervals, according to AFP journalists and witnesses on the scene.

President Mahamat Idriss Deby Itno said people had been killed and wounded in the blaze, without giving precise figures.

"Peace to the souls of the victims, sincere condolences to the grieving families and a speedy recovery to the wounded," Deby wrote on Facebook, promising to open an investigation into the fire.

The sky burst into flames above the Goudji area, where the army's largest depot of ammunition is located, for several hours before tapering off and finally ceasing after midnight.

- Roof blown off -

The explosions shook buildings as far as seven kilometres (four miles) away and the flames were visible for miles.

"The roof of our house was blown off by one of the explosions," said resident Kadidja Dakou, who lives in the Amsinene area near Goudji.

The 36-year-old and her three children took refuge in the street alongside their neighbours, for fear their houses would collapse, she told AFP by phone.

Authorities had cordoned off the area with a heavy security presence, where thick red smoke hung in the air long after the blasts stopped.

Foreign Minister Abderaman Koulamallah, who is also the government spokesman, said on Facebook that there were "huge explosions" at the site and urged the population to keep calm.

There are multiple homes in the neighbourhood that is the site of the depot, which sits near the international airport and a base where French troops are stationed.

The blaze "caused explosions of ammunition of all calibres", an official with the French forces told AFP on condition of anonymity.

"For the moment, no French military personnel have been wounded", he said.

Chad's president officially won 61 percent of a May 6 vote that international NGOs said was neither credible nor free and which his main rival called a "masquerade".

Deby was proclaimed transitional president in April 2021 by a junta of 15 generals after his father, president Idriss Deby Itno, was shot dead by rebels following 30 years in power.

Chad, one of the world's poorest nations, is considered vital in the fight to stop the march of jihadists through the Sahel region.