'Die or go on,' say trapped migrants

An Afghan migrant holds his child after they arrive at the port of Piraeus, near Athens.

Thousands of migrants were left stranded in Greece on Monday after Macedonia abruptly closed it border to Afghans, creating a fresh bottleneck as European countries scramble to respond to the continent's worst refugee crisis since World War II.

Overall, about 8 000 people were trapped on Greece's northern frontier and at the port of Piraeus after Macedonia introduced the measure on Sunday in a bid to stem an unrelenting influx of migrants.

Desperate to get through, hundreds of Afghans staged a sit-down protest in an area of no-man's land and occupied the railway line connecting the two countries, holding makeshift signs that read: "We can't go back" and "Why racism?"

Dozens of Afghan children also carried signs with the words: "Help us cross border." Greece said it would provide emergency shelter for the blocked migrants while working to find a solution with non-European Union member Macedonia.

Since November, countries on the Balkan route have allowed only Syrians, Iraqis and Afghans to continue their journey up towards Germany, Sweden and other European nations where they plan to apply for asylum.

Macedonia's decision to stop letting Afghans through came just two days after Austria controversially introduced a daily limit on asylum applications.