(Adds resignation of junior minister)
ROME, May 19 (Reuters) - Italian prosecutors are investigating the president of Sicily's regional government, a junior minister in the central government and other politicians for alleged corruption involving Sicilian ferry services, legal sources said on Friday.
According to prosecutors in Palermo, the island's capital, a group of politicians ensured favours for a local ferry operator in return for money and gifts in what prosecutors called "a system where corruption was almost the norm."
Simona Vicari, a junior transport minister from a small centrist party in Prime Minister Paolo Gentiloni's coalition, received a Rolex watch from a ferry operator in return for legislation that helped his business, the sources said.
After news of the investigation broke, Vicari said she was resigning in order to restore "greater serenity" to the government and to herself.
Ettore Morace, the head of the Liberty Lines ferry company, was arrested along with Girolamo Fazio, a former mayor of the Sicilian city of Trapani who is again running for mayor in the city in elections next month.
Vicari, whose brother works for Morace's company, ensured an amendment to the government's budget to reduce Value Added Tax on high speed ferries to 4 percent from 10 percent, the Carabinieri police said in a statement.
The president of Sicily's regional government, Rosario Crocetta, is accused of abetting corruption, according to the sources. He was not immediately available for comment.
The latest corruption scandal, involving politicians from traditional parties on the right and left, could fuel support for the anti-establishment 5-Star Movement at mayoral elections in Sicily in June and in regional elections there in November.
5-Star is currently the most popular party in Sicily, according to opinion polls, and is running neck-and-neck with the ruling Democratic Party nationwide. (Reporting by Antonella Cinelli; Writing by Gavin Jones; Editing by Mark Trevelyan and Hugh Lawson)