By Agence France-Presse
A fire broke out after the blast at around 9am (0800 GMT) in the city's 9th district, a residential and shopping area.
Images posted on Twitter showed debris covering the street and the lower part of the building blown out and in flames. Parked cars were also damaged in the blast.
An AFP photographer saw at least one person being carried away on a stretcher from the building by firefighters.
Firefighters worked to extinguish the blaze and exacuate some people from the building using ladders while emergency workers treated some of the injured at the scene.