Explosions that ripped through the city of Bujumbura after a fire in a military arsenal have killed several dozen people in the Burundian economic capital, security sources told AFP on Wednesday.

The explosions erupted late on Tuesday at the main ammunition depot of the Burundi National Defence Force (FDNB) in Musaga, a southern suburb of Bujumbura.

An army spokesperson said the cause was an "electrical accident."

In videos seen by AFP, clouds of smoke loomed over the neighbourhood during the blast, sending panic through the city of more than a million people.

Army, police officers confirm deaths

"It is impossible to establish a toll for the moment, but dozens and dozens of people have been killed, and there are hundreds or even thousands of injured," a high-ranking army officer told AFP on Wednesday.

A senior police officer present at the site said the detonation broke out "where heavy weapons and ammunitions are stored, which is why we immediately heard large explosions."

"There are dozens of dead, but the toll may be higher," the senior police officer said.

The arsenal in Musaga is located in a densely populated area and adjoins the Higher Institute for Military Cadres (ISCAM), where aspiring army officers are trained and housed.

Inmates among the victims

It also houses numerous army logistics depots and is next to another military base, Muha camp, and the central Mpimba prison.

A source at Mpimba prison told AFP that eight inmates died and several others injured. The injured were taken to hospital by the Red Cross early on Wednesday.

Authorities have yet to provide casualty figures.

Spageon Ngabo, director of the online bloggers' platform Yaga Burundi, said around 10 deaths had been reported by citizens to his organisation.

Burundi cautions citizens

The senior police officer, who joined the firefighting team late Tuesday, said property had been destroyed by the "massive inferno" and that the "base camp was reduced to ashes."

On Wednesday afternoon, fire and smoke could still be seen, according to the police officer. Residents in surrounding neighbourhoods fled their homes at night, the officer said, as fire-triggered projectiles landed nearby.

President Evariste Ndayishimiye, in a message on X, expressed his "sympathy" to "all those who have been victims of the fire."

Burundian authorities have urged citizens to report unexploded munitions by phone, warning: "Be careful and do not touch."

On social media, dozens of posts showed children being searched for by parents who lost track of them while fleeing.