The bodies of the African migrants were spotted Saturday afternoon off the coast of Ben Guerdane in southern Tunisia, said the civil defence official.
The report came after coast guards on Sunday rescued 17 Tunisians who had been trying to make their way to Europe on a rubber dinghy, according to the defence ministry.
The boat broke down off the northern coastal town of El Haouria, a spokesman said.
Tunisian and Italian authorities have been at the forefront of rescue efforts for a flood of mainly African migrants fleeing conflict in Libya and bound for Europe on unseaworthy boats that run into trouble.
In June, Tunisia's navy rescued 356 migrants, mainly Africans but also including Syrians and Pakistanis who had left Libya on a makeshift vessel on their way to Europe.
People smugglers have taken advantage of the chaos gripping Libya since the 2011 uprising toppled dictator Moamer Kadhafi to step up their lucrative smuggling business.
But the Mediterranean crossing is perilous and hundreds of migrants have died trying to reach Europe this year alone, while more than 20,000 have reached Italy since the beginning of the year.