The crossing from Greece to Macedonia has turned into a bottleneck on the Balkan migration route, with around 2,000 people being held up under new admissions rules, Greek state radio reported Monday quoting police.
Facing the freezing cold, migrants were forced to spend the night in buses, with witnesses counting 39 buses south of Idomeni, the village on the Greek side of the border point.
Following the lead of Slovenia, Croatia and Serbia further north on the route, Macedonia since last week has granted passage only to Syrians, Iraqis and Afghans who declare intent to seek asylum in Austria and Germany.
This has slowed processing at the border, creating the bottleneck.
People meanwhile continued travelling across the Aegean, reaching Greek islands from the Turkish coast even as Athens on Monday was facing mounting pressure from other EU countries to get a better handle on migration flows.
On Monday, 1,481 arrived in Athens from Lesbos and Chios, the coast guard said.
The countries on the Balkan route imposed restrictions after Austria announced last week it would accept only a limited number of asylum seekers through 2019.
Slovenia, Croatia, Serbia and Macedonia worry that if western Europe limits the number of asylum seekers it accepts, they may end up bearing the brunt of migrant influx.
Around 1 million people passed the Balkan route in 2015, according to the International Organization for Migration. With more than 36,000 arriving in the first three weeks of this year braving the deadly weather, there is no sign of the rate dropping.