"Some 50 vehicles were involved in the pile-up. We can confirm there were casualties," a police spokeswoman Anita Leskovec told AFP without elaborating.
Public Radio Slovenija quoted unofficial sources as saying at least five people died and several more had been injured in the accident which happened early in the afternoon near Senozece, around 60 kilometres southwest of Slovenian capital Ljubljana.
Due to the accident, the highway connecting the Adriatic coast with Ljubljana remained closed for several hours.