Social affairs minister Aleksandar Vulin said Serbia will take Croatia to global courts if the border crossings remain closed, arguing that Croatia should have been prepared for the influx.
With the flow into Croatia reaching more than 13,000, Prime Minister Zoran Milanovic warned matters were out of control and that his government would no longer be able to register or accommodate the migrants.
Croatian authorities deployed riot police to the Serbian border in a bid to stop migrants pushing into the country following the arrival of more than 6,000 people since Wednesday.
Many hundreds have pushed through border guard lines and are now continuing their way through Croatia on a journey to western Europe.
The controls are legal under Europe’s Schengen agreement, which allows free travel throughout the majority of the European Union , and they will only be temporary to handle the refugee crisis.
After bus trips through Serbia, the refugees crossed fields on foot to enter Croatia, where dozens of police directed them to trains and buses heading to refugee centres.
On Thursday, Croatian Interior Minister Ranko Ostojic said his country was “absolutely full”. When buses finally arrived, groups charged towards them, overwhelming Croatian police.
UN Secretary-General Ban Ki-moon has criticised Hungary’s treatment of migrants as unacceptable after police fired tear gas and water cannon at asylum-seekers at its border with Serbia.
Hundreds were involved in clashes at the Hungary-Serbia border on Wednesday, trying to breach a razor-wire fence.
Slovenia said it was ready to provide shelter and humanitarian care for 5,000 refugees but stopped people from entering from Croatia.
Migrants talk at the railway station in Beli Manastir, near Hungarian border, northeast Croatia, early Friday, September 18, 2015. “I think the extent that families are going to get to the next border shows you that’s what’s behind them is worse than what’s in front of them if they’re willing to continue to do this and continue to try”.
“Returning back to our country is impossible, because we have no financial means or the moral strength to go back home”, Abu Mohamed who fled Idlib in Syria, told The Associated Press.
Serbian officials, fearing the closure in Croatia would block thousands of migrants inside the country, protested Zagreb’s move.
Croatia, the EU’s newest member, says it will not halt their passage.