Migrants rescued at sea by the Italian navy and a charity ship disembarked in Italy on Friday, despite far-right Interior Minister Matteo Salvini's "closed ports" policy.

Thirty-six people plucked from a floundering boat off Libya by a navy patrol boat on Thursday were brought to Sicily after four European countries agreed to host some of them.

Another 30 people rescued by the Mare Jonio charity ship in a separate operation - including three women and a one-year-old girl - were disembarked on the Italian island of Lampedusa.

Salvini had initially refused to open Italy's ports to the migrants.

The interior ministry said it was opening an investigation into aiding illegal immigration and impounded the Mare Jonio, which is charted by the left-wing collective Mediterranea.

The ship was impounded in March after bringing rescued migrants to Italy, but released after a week. The Italian coast guard ruled declared the vessel unsuitable for rescues last month.

Rome's populist government has taken an increasingly hard line on migration, and Salvini, head of the anti-immigrant League party, last month signed a new directive banning charity vessels from rescuing migrants off Libya.

Mediterranea said Friday that the Mare Jonio had entered Italian territorial waters near the island of Lampedusa, where it was met by two police patrol boats for controls.

In the meantime, on Friday, a boat carrying up to 70 migrants from sub-Saharan Africa was reported to have sunk in the Mediterranean, leaving three people dead and dozens missing, Tunisian officials said.

The bodies of three people who drowned in the accident were found Friday, a spokesman for the Tunisian defence ministry said, adding the boat left Zwara on the northwestern Libyan coast on Thursday.