The United Nations and aid groups report that three Balkan countries have implemented more stringent screening policies for refugees, allowing only people with documentation proving they are from Syria, Iraq or Afghanistan to pass through their borders.
The move this week by Croatia, Macedonia and Serbia raised concern that refugees from other countries with bona-fide asylum cases could be turned back, leaving their immediate security up in the air, and their futures in limbo.
According to the office of the UN High Commissioner for Refugees, between 2,000 and 3,000 people were stranded in the Greek town of Indomeni, along the border with Macedonia. William Spindler, a spokesperson for the agency, said that several hundred had been turned away since Wednesday evening based on their nationality or lack of proper documentation proving they are from Syria, Iraq or Afghanistan.
"People from any other nationality were being denied entry, and this is causing frustration and tension between the different nationalities," said Spindler. Many of those who were prevented from entering Macedonia were from Iran and Morocco.
Farther north, some 300 people had been turned away by at Macedonia's border with Serbia.
"There were a number of Iranians, Bangladeshis, Pakistanis, but there were also some Moroccans and some Somalis," said Spindler.
The UN reported that Croatia had implemented similar policies, but that the restrictions had affected fewer refugees and migrants.
Europe's migrant and refugee policies have come under intense scrutiny after coordinated terror attacks took the lives of 129 people in Paris last Friday. Though all of the attackers who have been identified were European citizens, French Prime Minister Manuel Valls said on Thursday that several "took advantage of the refugee crisis," to "slip in" to Europe. It was not immediately clear if that meant they had returned from Islamic State-controlled areas posing as refugees. More than 800,000 refugees have arrived in Europe this year, about half of them fleeing the war in Syria.
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In a statement released on Thursday, the aid group Doctors Without Borders said that Serbian border guards had begun on Wednesday evening to stop people from crossing into the country from Macedonia. Only those with papers indicating they were Iraqi, Syrian or Afghans were allowed through.
"We're extremely worried about the latest developments and fear that people will be stranded without any assistance, shelter and food, just as winter sets in," said Stephane Moissaing, head of the organization's operations in Serbia. Those who were turned away had been offered little information or assistance, said Moissaing.
In the Southern Serbian city of Presevo, MSF, as the group is known by its French acronym, said it sheltered 20 people in a tent on Wednesday night, and that between 50 and 60 were waiting to enter from Macedonia in the early afternoon on Thursday. Among those who were turned away On Wednesday were women from Somalia and from Afghanistan who lacked proper documentation. One of the Afghan women was reportedly pregnant.
Citing reports from aid workers, the Financial Times reported on Thursday that roughly 200 people were staying on the frontier inside temporary structures provided by the UN's refugee agency.
"It is not acceptable that people who want to seek asylum are being segregated by nationalities," said Moissaing in a statement. "The right to asylum is universal and cannot be connected to certain nationalities."
"We fear that the closure of borders for certain nationalities may result in people resorting to even more dangerous routes to reach their destinations," he added.
Meanwhile, in the US, the House of Representatives on Thursday approved a bill making it harder for refugees from Syria and Iraq to be approved for entry. The bill, which would require intelligence agencies to individually certify that refugees do not pose threats to the US – a threshold that the Obama administration said was impossible to reach – was passed by a vote of 289-137. Should the bill pass the Senate by a similar margin, legislators would be able to override Obama's promised veto of the text.
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The US has received fewer than 2,000 Syrian refugees since the start of the country's civil war, a far cry from the numbers in Europe. The crisis on the continent appeared likely to worsen on Thursday evening, with the revelation that terrorists may have traveled along migrant routes. Valls said that Europe had to improve its border controls, a suggestion that called into question the Schengen zone arrangement, which allows travel with no passport among 26 European nations, not all of them members of the European Union.