The capital, Zagreb, was blanketed with snow early on Tuesday with occasional tree branches falling on parked cars.
In Slovenia, the STA news agency reported long lines forming on the main highways due to delays. Authorities say winter equipment for vehicles is mandatory.
Traffic official Andraž Vidmar said trucks have been redirected to side roads, creating traffic clogs there.
The snowy weather is expected to spread further east in the Balkans later in the day and on Wednesday, bringing freezing temperatures.
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