<p>Countries along the Balkan migration trail have begun refusing to admit people of certain nationalities, amid a backlash against refugees in the aftermath of the Paris attacks last Friday.</p> <p>Humanitarian workers active along the borders of Croatia, Serbia and Macedonia reported that refugees and migrants from countries other than Syria, Afghanistan and Iraq were now being stopped, raising the spectre of a migrant logjam in Greece.</p> <p>The move comes after Slovenia, the most northerly country along the trail, suddenly tried to return 168 Moroccan migrants to Croatia on Thursday, in the first major development along the Balkan migration route since Hungary shut its border in September.</p> <aside class="element element-rich-link element--thumbnail"> <p> <span>Related: </span><a href="http://www.theguardian.com/world/live/2015/nov/19/paris-attacks-police-investigate-isis-mastermind-dead-st-denis-raid-live">Suspected Paris attacks ringleader Abdelhamid Abaaoud killed in St-Denis raid  latest news</a> </p> </aside>  <p>The decision sparked panic among the countries to Slovenias south, who feared that Slovenia was about to block access to anyone who could not easily prove their need for refugee status, and consequently turned back all migrants from Africa and southern Asia.</p> <p>Slovenia said on Thursday afternoon it had not made any permanent decisions, and promised to admit refugees as long as Germany and Austria continued to subsequently take them. But a police spokesman confirmed that Slovenia would discuss with its Balkan neighbours how to limit the flow of so-called economic migrants in the future.</p> <p>We absolutely need to provide protection to those who need it, whose lives are threatened, who are escaping war zones, said a spokesman for the Slovenian interior ministry. For others we will need to reach an agreement on how to respond. No country has limitless capacity, so the capacity should be for those whose lives are really in need.</p> <p> <br /></p> <p> </p> <p>For now, campaigners on the ground said <a draggable="true" href="http://www.theguardian.com/world/2015/sep/10/refugee-crisis-apart-from-syrians-who-else-is-travelling-to-europe">people from Africa, Iran, Pakistan and Bangladesh</a>  who collectively amount to <a draggable="true" href="http://data.unhcr.org/mediterranean/country.php?id=83">less than 10%</a> of the flow through the Balkans, according to the UN  were already trapped in limbo at the borders of Croatia, Serbia, and Macedonia, since the three countries did not want to risk the possibility of anyone being stuck on their territory.</p> <p>Mdecins Sans Frontires (MSF) said Macedonia had begun to build a barrier along its southern border with Greece. A spokeswoman for the Macedonian interior ministry denied any such barrier was being built, but MSFs team leader on the border said it was clear that some kind of obstacle was being constructed. </p> <p>Its obvious that they want to do something, said MSFs Antonis Rigas. Every 20 metres theyve put out stones. What for? They havent started the construction, but Im an engineer, and I can say its there for something.</p> <p>Earlier in the week, Macedonias cabinet said it was considering whether to build a fence. But it claimed that such a fence, if built, would be used to block the passage of migrants only if upstream countries did the same, risking a bottleneck on Macedonian territory.</p> <p>Serbia has promised not to build a fence, but Slovenia is preparing one in order to better control the flow of refugees. Hungary completed work on a fence <a draggable="true" href="http://www.theguardian.com/world/2015/sep/15/refugees-scramble-fortress-europe-hungary-seals-borders">in mid-September</a>, causing the refugee route to swerve westwards into Croatia.</p> <p>Should the Balkan countries block the route entirely, Greece may be forced to deal with a logjam of refugees. An average of 4,750 people a day have arrived on its shores from Turkey this month, down from the October average of 6,800 but above the August daily rate of 3,500.</p> <p>Though their problems have received less attention than those of Syrians, many refugees from Africa and south Asia <a draggable="true" href="http://www.theguardian.com/world/2015/sep/10/refugee-crisis-apart-from-syrians-who-else-is-travelling-to-europe">claim to be fleeing human rights abuses</a>.</p> <p>A backlash against migrants and refugees has intensified after a passport used by a migrant to enter Greece in early October was found near the body of a dead bomber in Paris. Police are not yet sure <a draggable="true" href="http://www.theguardian.com/world/2015/nov/15/why-syrian-refugee-passport-found-at-paris-attack-scene-must-be-treated-with-caution?CMP=share_btn_tw">whether the passport holder was a the terrorist</a>. But the uncertainty has led to fears about the threat posed by thousands of undocumented migrants entering Europes south-eastern borders, <a draggable="true" href="http://www.theguardian.com/world/2015/nov/17/how-easy-is-it-to-buy-fake-syrian-passport">some of whom carry fake documentation</a>.</p> <p>A spokeswoman for the UN refugee agency, UNHCR, said the Balkan countries risked failing to uphold the UN convention on refugees should they begin to screen arrivals on the basis of their origin. </p> <p>It is important that every individual who is seeking asylum has access to a fair and efficient asylum procedure, regardless of their nationality, the spokeswoman said. UNCHR is monitoring the situation and recommending governments that each case is decided based on its predicaments not on the nationality of the asylum seeker. All countries along the Balkans route are signatories to the 1951 convention and UNHCR has been working with the government to build their asylum systems. </p> <p>Over 600,000 people have so far attempted to walk through the Balkans after landing in Greece in 2015.</p>