President Mahamat Idriss Deby Itno says there have been deaths and injuries but does not specify the number.
The fire began in N’Djamena’s Goudji district late on Tuesday and there had been “huge explosions” Foreign Affairs Minister Koulamallah Abderaman wrote in a statement on Facebook.
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.
A resident of an area near the depot said he saw three injured people on the street, and two of them were rushed to hospital on motorbikes.
Another resident said his neighbour, a shopkeeper, was killed after he was hit by a shell. On social media, people posted images of spent artillery shells that had fallen in nearby homes.
“Loud blasts woke us up,” resident Moustapha Adoum Mahamat told the Reuters news agency. “Our house was shaking as if someone were shooting at us. Then we saw a big fire at the military camp and smoke and things exploding in the air. We could see artillery fly over us.”
Kadidja Dakou, who lives in the Amsinene area near Goudji, told the AFP news agency she had run out onto the street with her three children for fear their house would collapse. Her neighbours did the same.
“The roof of our house was blown off by one of the explosions,” the 36-year-old said.
There are multiple homes in the neighbourhood where the depot is located. It is also near the international airport and a base for French troops.
The blaze “caused explosions of ammunition of all calibres”, an official with the French forces told AFP on condition of anonymity.