The Italian coastguard is holding three Maltese men on suspicion of having transported 19 migrants who landed in Sicily last night.
The Italian media said the three men, aged 43, 36 and 25, were arrested on a power boat after interception by coastguard launches.
Initial investigations showed the boat had left from Malta.
The Italian media have reported that the coastguard monitored the disembarkation of the migrants on radar and then gave chase, catching up with the boat in international waters. Warning shots were fired.
Data on the boat's GPS showed various points along the Sicilian coast, indicating that the boat may have been used on previous ferry trips.