Thirty-six people were plucked from a floundering boat off Libya on Thursday after they were spotted by a navy boat patrolling as part of an Italian operation to protect fishing and oil platforms.

"I thank France, Malta, Luxembourg and Germany for the solicitude with which, within a few hours, they said they were ready to welcome" some of them, Prime Minister Giuseppe Conte said in a statement.

The left-wing collective Mediterranea, which charters the Mare Jonio charity ship, rescued 29 people in distress in a separate operation off Libya on Thursday, including three women and a one-year old girl.

"For them, the ports will remain closed", Italy's far-right Interior Minister Matteo Salvini said.

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.