A boat carrying up to 70 migrants from sub-Saharan Africa has sunk in the Mediterranean.

Officials say three people have been confirmed dead with dozens more still unaccounted for.

The bodies of three people who drowned in the accident were found earlier today, a spokesman for the Tunisian defence ministry said, adding the boat left Zuwara on the north western Libyan coast on Thursday.

A fishing boat picked up 16 survivors, who were transferred on board one of three military vessels involved in the search and rescue operation.

A helicopter was also mobilised, the defence ministry said, adding that between 60 to 70 people were believed to be on board.

Interior ministry spokesman Sofiene Zaag said however around 75 people are believed to have been on board the Italy-bound boat when it departed Libya.

Italy's far-right Interior Minister Matteo Salvini has vowed to close the country's ports to migrants, although earlier Friday dozens who had been rescued at sea disembarked in Sicily.

The Mediterranean is the "world's deadliest sea crossing" according to the United Nations refugee agency, with one person in 14 dying on the route from Libya to Europe last year.