Italy's Interior Minister and Deputy-Premier Matteo Salvini attends a news conference after meeting Hungary's Prime Minister Viktor Orban, in Milan, Italy, Tuesday, Aug. 28, 2018. (AP Photo/Luca Bruno)

Rome - Italian prosecutors on Friday told Interior Minister and Deputy Premier Matteo Salvini that he is under investigation for "kidnapping" a group of migrants.

The case concerns about 150 migrants who last month were rescued and taken to a Sicilian port by the Italian coastguard, but were denied disembarkation rights for several days by Salvini.

Salvini theatrically opened a letter with an official notice from Palermo Chief Prosecutor Francesco Lo Voi in a live Facebook video.

The minister claimed he risked "at least 15 years in prison" and said he was ready to be interrogated, but promised his social media followers he would "not give an inch."

Previously, Italian media reported that Salvini was also being probed for illegal arrest and abuse of power, but he was not notified of any such charges.

Despite being under investigation, there is little chance of the leader of the far-right League facing a trial, as he enjoys parliamentary immunity, which is unlikely to be lifted by pro-government parties.

Meanwhile, a majority of the migrants aboard the Diciotti ship, who were eventually allowed to disembark on August 25 and were taken to reception centres in Sicily and near Rome, have gone missing.

According to Salvini, this proves they were not genuine refugees. Others have pointed out that the migrants had no legal obligation to stay in a fixed place.