Volunteers from Greece and the Netherlands handed out sanitation kits and emergency supplies, while vendors from cell phone companies sold SIM cards. Hungary's prime minister has called for a national referendum on the European Union's plan for a mandatary quota for the resettlement of migrants and refugees. Greece's migration minister says he expects the number of stranded immigrants in Greece to reach "tens of thousands" after Balkan countries introduced stricter transit rules. Greece, he said, was applying diplomatic pressure on European Union and NATO allies to limit unilateral actions by EU member states to restrict entry to asylum seekers and to make recently deployed patrols by the military alliance in the Aegean Sea more effective. The interior ministry said about 12,000 people have been stranded in Greece since neighbor Macedonia began turning Afghan immigrants away at the border and slowing the number of crossings for others heading to central and northern Europe. The United Nations High Commissioner for Refugees, Filippo Grandi, is in Athens to meet government officials Wednesday, including Prime Minister Alexis Tsipras. The German government says 125 Afghans who had their asylum applications rejected have voluntarily returned to their homeland. Martin Schulz says in an interview with French radio Europe 1 that the move, announced Tuesday by Belgian interior minister Jan Jambon, was carried out according to the rules of the Schengen borderless zone, which he said permits states to temporarily restore border controls. Amnesty said in its 2015-2016 annual report released Wednesday that "the EU's failing refugee strategy remains focused on keeping people out, rather than providing the safe passage to Europe that could save thousands of lives." The human rights group said EU countries "for the most part vacillated or actively obstructed potential solutions" to sharing refugees. Sebastian Kurz says that Greece has "clearly expressed no interest in reducing the (migrant) influx and in contrast wants to continue waving them through" to Macedonia, from where they make their way northward. The statement by Kurz comes ahead of a meeting Wednesday of Austrian and West Balkan government ministers in Vienna aiming at finding common solutions to crimping the refugee flow.