Trucks carrying wire fencing arrived in the Slovenian village of Veliki Obrez close to the border with Croatia early on Wednesday, a day after the government said it would start erecting barriers to control the flow of migrants.
Large numbers of soldiers and police were at the scene, some guarding construction equipment. Slovenia is the smallest country on a major route for refugees and migrants heading north on their way to Austria and then Germany.
About 180,000 people, many fleeing war in Syria and Afghanistan, have entered the Alpine state since mid October, when Hungary fenced off its border with Croatia and pushed the migrant route towards it western neighbour.
Prime Minister Miro Cerar said on Tuesday the border would remain open, but the fence would help control the flow of people.
He said his country would not have the resources to shelter large numbers of migrants over the harsh winter if Austria shut its border, creating a bottleneck.
About 175 policemen from other EU states have come to Slovenia to bolster the local force, with another 100 expected in the next two weeks.
Cerar's decision comes after fourteen people died and a further 27 were rescued by Turkish authorities after their boat sank on its way to the Greek island of Lesbos, Dogan news agency reported on Wednesday.
Children were among those who died when the wooden boat went down in the 8km (5 mile) stretch of water separating Lesbos from the Turkish coast, Dohan reported. Turkey's coastguard was not immediately available to comment.
European and African leaders are due to meet Wednesday in Malta to discuss the migrant issue, with the EU hoping that pledges of cash to some of the world's poorest countries will help discourage others from making the journey.
The European Union expects a battle at the summit of world leaders in Turkey on Sunday to have its migration crisis recognized as a global problem needing a global response, an EU official said on Tuesday.
