About 300 migrants have staged a sit-in on railway tracks connecting Greece and Macedonia, forcing a train to turn back. Refugees say the country's entry limits are now too stringent.
The migrants, many of them with children, carried slogans reading "Open the borders, no food" and "We are humans, not animals," during their protest, which cut off the railway line between northern Greece and Macedonia.
"I'm 17 days on the road with my family and my two children. I don't know what to do," one Syrian man lying on the rail tracks with his children told the Athens News Agency.
The migrants say Macedonian authorities have backtracked on a plan to let in 580 people a day after the border was closed on Friday and only 300 Iraqis and Syrians were allowed in on Saturday.
Their protest forced a cargo train on its way to central Europe from Greece to turn back.
More than 7,000 refugees are stranded at a tent camp in the Greek border town of Idomeni, after Macedonia once again introduced strict border restrictions.
Observers said the bottleneck was expected to worsen after EU members Slovenia and Croatia, as well as Serbia and Macedonia, imposed a daily limit of migrants and as Athens warned the number of people "trapped" on its soil could more than triple next month as the weather improves.
"We estimate that the number of those trapped will reach from 50,000-70,000 people next month," Greek Migration Minister Yiannis Mouzalas said.
The so-called Balkan route is heavily used by refugees trying to reach richer Western Europe.
Austria, Hungary react
Meanwhile, Austria accused Greece of failing to adequately police its borders as part of Europe's Schengen passport-free zone.
But Mouzalas said Austria's politicians were talking with one eye on the electoral calendar as a presidential poll is due in April.
Austria has also introduced a daily cap of 80 asylum seekers and said it would allow just 3,200 migrants to transit the country per day.
Also on Sunday, Hungary ordered the construction of a new fence along the border with Romania to prevent migrants from entering.
The Budapest government has already built fences on its borders with Serbia and Croatia.
mm/jlw (AFP, AP, dpa)