Macedonia is the last country on the Balkan migrant route which on Wednesday imposed a stricter border regime for migrants en route to Western Europe.
The Macedonian police said they closed the border with Greece, which left hundreds of people blocked in Greece.
"The border is closed," a Macedonian senior police official told Agence France-Presse, while a Greek police spokesman said the border had been closed since Tuesday night and that about 600 migrants from Syria, Afghanistan and Iraq were on the Greek side of the border, waiting to cross into Macedonia.
Austria today imposed restrictions on the reception of refugees and migrants arriving via Slovenia. Slovenia, Croatia and Serbia announced similar measures.