Migrants saved by non-governmental organisations (NGO) boats will not be allowed into Italy, said rightwing Interior Minister Matteo Salvini.
Mr Salvini has often accused the NGOs of encouraging the trafficking of migrants. He told Corriere della Sera these NGOs were no longer "legitimate".
He also hailed the agreement reached by European Union leaders in Brussels that Italy hopes will lessen its burden, reports BBC.
Thousands of migrants, mainly from African countries, have reached Italy.
The number is 95 per cent lower than at the peak of the crisis in 2015, the EU says, but started to rise again recently.
Several Central European states have so far rejected an EU scheme to relocate 160,000 refugees from overcrowded camps in Greece and Italy.
Mr Salvini posted an image on his Facebook, showing one of the rescue boats, with the hashtag #closetheports.
His message read: "Halt the mafia of human trafficking: the fewer that depart, the fewer will perish."
Italy has complained about the lack of solidarity and its new government sparked a crisis earlier this month when it did not allow a boat full of migrants, the Aquarius, to disembark. Spain agreed to take them after days at sea.
The Brussels summit agreement foresees the creation of secure centres to receive migrants in EU countries on a voluntary basis - but it does not specify where.
President Emmanuel Macron of France, for instance, said hours after the deal that they would be in countries where migrants arrived first - such as Italy and Greece, but not France.
Italy insists these may be set up anywhere in the EU.