Police in Croatia said they have intercepted a group of 10 migrants in a dense forest, and another two who had apparently died en route.
The group who entered the country illegally were found after a tip from locals, police in the central town of Karlovac said.
Police said they have opened an investigation about the deaths and did not specify any of the migrants' nationalities.
Local media said they are likely to have been killed in a landslide in rugged terrain after they crossed from neighbouring Bosnia.
Several thousand migrants remain stuck in Bosnia as they aim to reach the wealthy nations in Western Europe.
Migrants often first try to cross to European Union member Croatia.