At least four people have been killed by a series of powerful explosions at an ammunitions depot in Burundi's largest city, Bujumbura, local residents have told the BBC. The blasts erupted late on Tuesday at the facility, located in the suburb of Musaga, due to an electrical fault, an army spokesperson said. Shrapnel and debris were propelled more than 5km (three miles) and several houses in nearby districts were destroyed by the force of the explosions. The authorities have not yet provided any casualty figures but family members and eyewitnesses told the BBC of four separate deaths in the city. The AFP news agency quotes security sources as saying that dozens of people had died. One woman told BBC Gahuza that a relative, who had been detained at Mpimba Central Prison, had died after a bomb hit the facility. Numerous inmates at the prison, which is located near the ammunitions store, are reported to have been injured. In the north-eastern neighbourhood of Gisandema, witnesses told BBC Gahuza that a bomb had destroyed a house and killed a domestic worker. The authorities have said they cannot yet comment on the number of casualties as they are still assessing the extent of the damage. The explosions sent plumes of smoke rising above the city, sparking panic in the city of more than a million people. President Evariste Ndayishimiye, in a message on X, expressed his condolences to all Burundians, adding that the authorities are 'here to help'.