Croatia closed all but one of its border crossings with Serbia after straining to cope with more than 13,000 migrants who have entered the country after Hungary closed its border.
Huge numbers of people surged into Croatia after Hungary erected a barbed wire-fence and took other tough measures to stop them from using it as a gateway into Western Europe.
Croatia represents a longer and more difficult route into Europe, but those fleeing violence in their homelands had little choice.
Many of the migrants are Syrians and Iraqis fleeing war, who are seeking safety and prosperity in Germany and elsewhere in Western Europe.
Serbian officials, fearing the closure in Croatia would block thousands of migrants inside the country, protested Zagreb's move. Aleksandar Vulin, Serbia's social affairs minister, said Serbia will take Croatia to international courts if the international border crossings remain closed, arguing that it should have been prepared for the influx.
"We will not pay the price of someone else's incapability," Vulin said. "I am sorry to see that Croatian humanity and solidarity lasted just two days."
However, despite the border closures, many continued entering Croatia through cornfields. Women carrying children and people in wheelchairs were among the thousands rushing in the heat in hopes of finding refuge.
One of the more desperate situations was unfolding in the eastern Croatian town of Beli Manastir, near the border with Hungary. Migrants slept on streets, on train tracks and at a local petrol station.
People were scrambling to board local buses, without knowing where they are going.
Hungary's Prime Minister Viktor Orban says that his country has started building a razor-wire fence along a stretch of its border with Croatia to keep migrants from entering the country there.
The migrants would prefer the quicker route to Europe through Hungary, instead of taking the longer route to Western Europe through Slovenia.
Orban says the first phase of the 41-kilometer (25 mile) barrier will be completed on Friday, with coils of razor wire in place before an actual fence goes up.
Meanwhile, Slovenia has been returning migrants to Croatia and has stopped all rail traffic between the two countries. Slovenian police have intercepted dozens of migrants who tried to cross through the forests overnight into the country from Croatia and will be returned there.
As the sun rose on Friday, refugees from Syria, Iraq and Afghanistan woke up to a new day with no hope in sight.
