29 other individuals were rescued, it added.
The boat went down in waters off the city of Abwabed, which is close to Sfax, where African migrants sometimes depart.
According to national guard official Houssem Eddine Jebabli, search efforts were in progress for potential missing persons.
Amidst an unparalleled migrant crisis, Tunisia has supplanted Libya as a primary destination for Africans and others seeking a better life in Europe.