Thousands of migrants, newly arrived in Greece from Turkey during the weekend, crowded the Athens port of Piraeus Monday, even as the Balkan countries they must traverse to reach wealthier parts of Europe pushed their gates further shut.
More than 4,000 people were ferried to Athens from Aegean islands on Monday. Most are looking to continue their journey across Macedonia, Serbia, Croatia, Slovenia and then Austria, with Germany their final goal.
Local media reported, however, that buses that were supposed to take them to Greece's north did not show up, in an apparent effort by Greek authorities to prevent a potentially volatile massing of people on the border with Macedonia.
The Greek minister in charge of migrants, Ioannis Mouzalas, told state TV late Sunday that more than 5,000 people were stuck at the border with Macedonia without a clue as to whether or when they may be allowed to continue.
Macedonia, meanwhile, confirmed that it is now only allowing Syrian and Iraqi refugees through, matching a decision by its northern neighbour, Serbia.
Until now, Afghans have also been allowed to pass through with only limited controls.
Fearing that Austria may close its border to migrants, the countries on the so-called Balkan route have since late November successively adopted measures to prevent a pile-up on their soil.
The measures include a barrier to all economic migrants and tighter controls on the borders.
International aid organization workers have been expressing concern that sealing borders will provide fuel for traffickers who charge the migrants for an often dangerous sneak across borders.
Around 1 million people, many of them refugees from war zones in the Middle East, passed along the Balkan corridor during the past 12 months. Virtually all continued to Germany and other wealthy European nations.