The European Union's migrant strategy suffered a major new setback Friday with Italy refusing to freely accept people rescued at sea and Libya spurning a proposal for asylum processing centres.

The salvoes follow a fractious EU summit in June which agreed to set up "disembarkation platforms" outside the bloc to process migrants after Italy's new populist government said it was closing its ports.

"Italy does not want to be the only country where migrants saved at sea by its own naval units disembark," Foreign Minister Enzo Moavero Milanesi said in a letter to EU foreign policy chief Federica Mogherini.

The Italian position and its implications will be discussed at a meeting later Friday by member states in Brussels, EU sources said.

Libyan Prime Minister Fayez al-Sarraj meanwhile rejected the EU proposal for asylum processing centres in his country, saying: "We are strictly against Europe officially placing illegal migrants who are no longer wanted in the EU in our country."