The Balkans struggled with a growing backlog of migrants yesterday after Hungary sealed its southern border and Slovenia tried to impose a limit, leaving thousands stranded on cold, wet borders where tempers frayed.

Having declared it would accept only 2,500 per day, Slovenia said 5,000 had arrived from Croatia yesterday, with another 1,200 on their way by train.

“Croatia is ignoring our pleas, our plans,” Bostjan Sefic, state secretary at Slovenia’s Interior Ministry, told a news conference, saying the army would be called in to help if such a rate continued.

Attempts by Slovenia to ration the flow since Hungary sealed its border with Croatia at midnight on Friday has triggered a knock-on effect through the Balkans; Croatia began holding back new arrivals and Serbia said it may do the same on its border with Macedonia.

More than 10,000 were stranded in Serbia, the United Nations refugee agency (UNHCR) said, with more on the way but nowhere to go.

Groups of migrants fought with each other in the morning, aid workers said, after a night spent under open skies lashed by autumn wind and rain.

“Open the gate, open the gate!” they chanted, their passage barred by lines of Croatian police who erected an improvised fence to control access. Police began letting through one busload an hour.

Slovenian army may be called in if such a rate continues

Slovenia has found itself dragged into the path of the greatest migration of people in Europe since World War II after Hungary sealed its border with Croatia to migrants on Friday.

A country of two million people bordering Hungary, Italy, Austria and Croatia, Slovenia said it would only allow in as many as it could register, accommodate and send on to Austria.

It said Austria had limited its own intake, something Vienna denied.

Most refugees want to reach Germany, which for the moment is letting them enter. Slovenia’s Sefic said Austria was experiencing “big problems” in handling the numbers and that Germany was accepting fewer.

What initially looked like a smooth and well-coordinated response by fellow ex-Yugoslav republics Slovenia and Croatia quickly broke down into the kind of discord and disarray that has characterised Europe’s response to the hundreds of thousands reaching its shores by boat across the Mediterranean and Aegean seas, many of them Syrians fleeing war.

Serbia’s minister in charge of migration suggested Serbia too may try to stem the flow from Macedonia, proceeding at a rate of around 5,000 per day.

“We have to think about how many people we can take in under such conditions,” Aleksandar Vulin told reporters in Berkasovo. “Let’s not blame Serbia when the entire EU is turning its gaze from what’s happening here.”

Hungary’s right-wing government says the mainly Muslim migrants pose a threat to Europe’s prosperity, security and “Christian values”, and has sealed its borders with Serbia and Croatia with a steel fence and new laws .