Amateur video broadcast on BFM-TV showed clouds of dust in the street and bystanders covering their mouths with their sleeves.
Images of the two buildings before the collapse indicate one used to have five floors and the other six.
As noted, one of the collapsed buildings were in disrepair, its inhabitants were evicted.
In a tweet, the regional authority said police and firefighters were both at work at the site and urged Marseilles residents to avoid the area.
Quoted as saying by local media, Sabine Bernasconi, the local mayor of the 1st and 7th districts of Marseille, said one of the buildings was in poor condition and had been subject to an evacuation order.