Human traffickers increasingly use Tunisia as a launch pad for migrants trying to make their way to mainland Europe.
Thirty-five migrants have died and 67 others rescued after their boat sank off the Tunisian coast.
The rescue of more people, who are of Tunisian and other nationalities, is ongoing, the ministry said.
Security officials said the boat was packed with about 180 migrants, including 80 from other African countries.
Tunisia’s interior ministry reported a distress call at 10.45pm on Saturday night from “a fishing boat about to sink” with migrants on board.
Tunisians and seven foreigners were among the survivors, including nationals from Ivory Coast, Mali, Morocco and Cameroon, said a defence ministry spokesman.
He added: “The coastguard and the navy continue their search with the support of a military plane.
“Units of the Sfax Marine Guard and the Navy went to the boat which was five nautical miles from Kerkennah Island and 16 nautical miles from the city of Sfax.”
Human traffickers increasingly use Tunisia as a launch pad for migrants heading to Europe.
Unemployed Tunisians and other Africans often try to depart in makeshift boats from Tunisia to Sicily in Italy.
Nine migrants, including six children, drowned in boat accident off Turkey’s Mediterranean coast early on Sunday morning.
The boat capsized near the town of Demre in the southern province of Antalya, according to the Turkish coastguard.
