The legal summons to mayors and shutting down of pro-referendum websites signal stepping up of efforts by Spain to block the referendum bid.
Seven men were found dead during Saturday’s rescues, but survivors brought to Trapani in Sicily indicated a further 13 had been lost at sea.
The new deaths add to a toll of 1,222 on the route as of May 10, compared with 966 by the same date last year, according to IOM calculations.
Italy has become the main arrival point in Europe for people fleeing persecution and poverty in Africa, most of them crossing the Mediterranean from Libya.
Italy set out plans on Monday to help people staying in temporary accommodation in central Italy after the fiercest earthquake in decades struck regions already rocked by repeated tremors in the past two months.
Several homes and churches were brought down when a 6.6 magnitude earthquake struck the same central regions of Italy that have been hit by repeated tremors over the past two months.
The Italian writer and performer, famous for his cutting political satire in plays such as ‘The Accidental Death of an Anarchist’, won the Nobel prize for literature in 1997.
Italy is currently the main point of entry for seaborne migration from Africa amid Europe’s worst migration crisis since World War II.
Italy is the last major Western country to legally recognise gay couples and an original draft law had to be heavily diluted due to divisions in Prime Minister Matteo Renzi’s ruling majority.