Belgrade, Serbia: Four nations along Europe’s Balkan refugee corridor shut their borders Thursday to those not coming from war-torn countries such as Syria, Afghanistan or Iraq, leaving thousands of others seeking a better life in Europe stranded at border crossings.

The overnight decision was exactly the domino effect that both asylum-seekers and European nations had feared would happen given the record number of people fleeing to Europe this year.

The UN refugee agency says three Balkan countries shut their borders overnight to refugees from nations that are not directly engulfed in war.

Macedonia was not allowing in from Greece people from Morocco, Sri Lanka, Sudan, Liberia, Congo or Pakistan, the UNHCR spokeswoman in Serbia, Melita Sunjic, said Thursday. Slovenia also said it has closed its border for the so-called economic refugees.

On the Serbian border with Macedonia, the Serbs were only letting in refugees from Syria, Afghanistan and Iraq. And on the Croatia-Serbia border, Croats were only accepting people from those three countries plus Palestine, she said.

Serbia has turned back to Macedonia some 200 refugees and Macedonia has not let them in, she said.

“So they are stuck on a no-man’s-land,” she told The Associated Press.

Croatia has refused 162 refugees rejected by Slovenia.

In the Greek border area of Idomeni, police said the border has essentially been shut down to all since about 8am after roughly 300 people, mostly from Iran, gathered at the crossing seeking to also be allowed through. A further 2,500 people are waiting at a camp nearby that provides temporary shelter for those heading north through the Balkans.

The partial closure of the borders could trigger huge pileups of desperate people along the Balkan corridor that has seen hundreds of thousands of people cross as they head to wealthy EU states, mostly Germany. Although Syrians are the biggest group among the asylum-seekers, tens of thousands of people fleeing poverty — such as Pakistanis, Bangladeshis or Sri Lankans — have also joined the surge.

Serbian Labour Minister Aleksandar Vulin on Thursday blamed EU-members Slovenia and Croatia for the ban, saying they have started turning back economic refugees, those fleeing poverty, not war.

“We have to protect our country. That is why we have applied reciprocal measures towards the people Slovenia and Croatia have no room for,” Vulin said.

Slovenia’s decision to start turning back people it considers economic refugees triggered the chain reaction along the Balkan refugee route. Slovenian media say 70 refugees from Morocco and Ivory Coast have been turned back by the Slovenes in the past few days.

Slovenian police spokesman Drago Menegalia said in recent days, “there is increased number of persons who were recognised as pure economic refugees” entering the small Alpine state from Croatia.

“These foreigners do not qualify for international protection,” according to EU laws, he said.

Slovenian officials say they will continue to allow the transit of refugees from war-ravaged countries such as Syria, Afghanistan and Iraq pass through on their way to Austria and other richer EU states.

Meanwhile, the Dutch government has debated internally and with its allies a plan to introduce passport checks at the borders of several Western European countries in a bid to control an influx of refugees and refugees.

The idea of carving out a “mini-Schengen” within the Schengen area would seem to violate the treaty guaranteeing free travel within 26 European countries.

The European Commission, the EU’s executive arm, has received no formal proposals regarding the creation of a “mini-Schengen” zone within the existing passport-free area, a Commission spokeswoman said on Thursday.

Europe is struggling to cope with its biggest migration crisis since World War Two.

German Interior Minister Thomas de Maiziere told a news conference in Berlin on Thursday that his Dutch counterpart had raised the idea with him, but Germany was not enthusiastic.

“Our political goal must be that the Schengen area as a whole functions,” he said. “Everything else would just be supplementary considerations.” The Dutch plan is separate from a French plan to introduce systematic border checks within the Schengen area as a security measure after the attacks in Paris last week.

The “mini-Schengen area” would include Austria, Germany, Belgium, Luxembourg and the Netherlands, and would involve setting up transit camps for refugees outside those borders, a report in newspaper De Telegraaf said.

Foreign Minister Bert Koenders confirmed those details in part to the paper, but said other measures were also under consideration.

“The Netherlands and other countries are talking about many different solutions,” said spokeswoman Janet Takens of the Justice Ministry, which oversees immigration policy.

“We are talking with like-minded countries on a regular basis,” she said, declining to provide details.

The leader of Prime Minister Mark Rutte’s conservative People’s Party for Freedom and Democracy in parliament said on Wednesday he supported the idea of a mini-Schengen, while the leader of junior coalition partner Labour said he sees “complications and obstacles” to the plan.

Marit Maij, a member of parliament for Labour, told Reuters her party could support the plan only if European border policy “continues to fail.”