Slovenia began erecting razor wire along its border with Croatia on November 11 to try to curb a record influx of migrants attempting to enter the country via the Balkans.
Slovenia last month became the latest favored point of entry for thousands of migrants heading to northern Europe after Hungary sealed its borders with Croatia and Serbia.
More than 180,000 have passed through the small European Union member state of two million people since mid-October, most headed for Germany, Austria, and Sweden.
"We have started erecting technical obstacles on the southern border in two areas," Interior Ministry spokesman Bostjan Sefic said at a news conference in Ljubljana.
The barriers near the towns of Brezice and Razkrizje will remain in place for six months, he said.
In total, Ljubljana plans to fence off 80 kilometers (50 miles) of its 670-kilometer (400 mile) frontier with Croatia, officials said.
The barrier is intended to direct the migrants toward registration centers, they said.