The coastguard rescued 20 migrants who had been on the overcrowded boat, which sank off Louata in Sfax region on Friday, the official told Reuters.
The coastline of Sfax has become a major departure point for people fleeing poverty in Africa and the Middle East for a chance at a better life in Europe.
In recent months, hundreds of people have drowned off the Tunisian coast, with an increase in the frequency of attempted crossings from Tunisia and Libya towards Italy.
In light of an unprecedented economic and financial crisis in Tunisia, more than 18,000 Tunisians travelled by boats to Europe in 2022, according to rights group Tunisian Forum for Economic and Social Rights.