Greece has warned that the number of migrants trapped on its soil could more than triple in coming weeks, reaching as many as 70,000, following border shutdowns throughout the Balkans.
"We estimate that we will have a number of people trapped in our country which will be between 50,000 and 70,000... I believe in the coming month," Migration Minister Yannis Mouzalas said on February 28.
He said some 22,000 migrants were already in Greece.
Greece is a primary gateway to Europe for tens of thousands of people fleeing war and poverty in the Middle East and beyond.
It has been inundated with migrants in recent days after four Balkan countries announced a daily cap on migrant arrivals.
Slovenia, Croatia, Serbia, and Macedonia imposed a limit of 580 migrants entering their borders each day.
Those measures follow moves by Austria to impose a daily cap of 80 on asylum applications and allow only 3,200 migrants to transit the country each day.
Athens accuses Vienna of unleashing a domino effect of border restrictions along the so-called "Balkan route," which migrants have been taking to get to wealthier northern European countries.
Austria and the Balkan countries, in turn, accuse Greece of failing to properly police its borders.
Some 120,000 migrants have already arrived in Europe so far this year, adding to the one million who made the dangerous journey across the Aegean Sea from Turkey in 2015, according to UN estimates.