Those identified were Belgian citizens Frans Rene Vandenbussche and Rudolpha Josepha Lauwers, both 61 years old, Barbara Patricia Brayden, 47, of Ireland, and 30-year-old Ivan Bencic from Porec.
The identity of another two persons killed in the crash has not been established yet.
Another Irish citizen, a woman of 49, was operated on at Pula's general hospital yesterday after sustaining serious injuries to her internal organs. Her condition remains critical.
The cause of the accident has not been determined yet.
The biggest crash on the Istrian Y to date happened around 7.15 am on Friday near Medaki, a village not far from Porec, a resort on Istria's central west coast, as Bencic, driving a Kompas travel agency van transferring tourists from Pula to Porec, crossed onto the left side of the road and smashed into a refrigerator lorry with Italian licence plates, whose driver sustained mild injuries.