Giorgia Meloni says Rome prosecutors have opened an investigation against her and two government ministers for repatriating a Libyan warlord wanted by the International Criminal Court.

Ministers believe there was no reason to open an investigation. Meloni supporters accused Rome's chief prosecutor of politicising the case and say it is part of a broader battle pitting magistrates against the government over planned judicial reform that will shake up Italy's creaking legal system.

Osama Elmasry Njeem, who was wanted for alleged crimes against humanity, was freed last week and flown home by an Italian state aircraft.