Macedonia has announced it will close its border with Greece, effectively blocking the Balkan route north.
The decision came after Slovenia barred access to refugees transiting Macedonia. Croatia and Serbia then said they would follow suit.
Some 13,000 refugees are now stranded at the Macedonia-Greece border.
The moves come after the EU and Turkey set out a plan to ease Europe’s biggest refugee crisis since World War Two.
Announcing the plan on March 7, European Council President Donald Tusk, had said there would no longer be a path to Europe for migrants.
“The days of irregular migration to Europe are over,” he said.
Hundreds of thousands of refugees have travelled through Macedonia over the past year, heading north.
However, Macedonia began to limit the numbers, first to Syrian, Afghan and Iraqi refugees, then recently to just a trickle – mainly Syrians from areas it considered conflict zones.
This created a bottleneck, with some 13,000 refugees now living in a sprawling camp at the Idomeni crossing.
Macedonia’s announcement came after Slovenia said on March 8 that it would allow in only migrants who planned to seek asylum in the country, or those with clear humanitarian needs.
Slovenian PM Miro Cerar said the country’s move meant that “the Balkan route for illegal migration no longer exists”.
Serbia then said it would close its borders with Macedonia and Bulgaria to those without valid documents.
“Bearing in mind that the new regime is implemented by a member of the European Union (Slovenia), Serbia cannot afford to become a collection centre for refugees,” it said in a statement.
Croatia announced similar measures. Interior Minister Vlaho Orepic said this was a “new phase in resolving the migrant crisis”.
Sebastian Kurz, the foreign minister of Austria, which itself has introduced caps on the number of refugees allowed through, welcomed the moves.