Clashes broke out again on Wednesday between Macedonian police and migrants stranded at the refugee camp in the Greek border town of Idomeni, Greek TV reported.
Footage from Idomeni showed police tossing teargas cannisters at dozens of migrants attempting to break through a border fence. The migrants withdrew and the situation calmed, but tensions are still high.
Around 300 migrants and two dozen police officers were injured in a similar incident on Sunday, when around 3,000 people attempted to force their way into Macedonia after having been stuck for more than a month at the overcrowded camp.
The path to wealthy EU countries in the north was blocked a month ago when Macedonia and other countries along the so-called Balkan migration route sealed their borders to a stream of migrants.
Last year, around 1 million people - mostly refugees from Syria and Iraq - applied for asylum in Europe, with Greece, Macedonia, Serbia, Hungary, Croatia and Slovenia having served as main transit countries.
Greece has bore the brunt of bottlenecks following the closures, although the European Union has brokered a deal with Ankara in a bid to reduce irregular migration to the bloc via the Aegean Sea.
The European Commission has also tried to take pressure off Greece by awarding it emergency aid and redistributing some of its asylum seekers to other member states. But the programme has had limited success, with only 615 relocated out of the country so far.
Meanwhile, the humanitarian situation in Greece has come under sharp criticism from human rights groups.
Pope Francis, a vocal champion of migrants, plans to assess the conditions himself on the Greek island of Lesbos on Saturday.
"Next Saturday I will go to the island of Lesbos, where over the past months many refugees have transited," the pope said during his weekly audience in St Peter's Square.
The prupose of his trip, he said, was "to express closeness and solidarity towards both the refugees and the citizens of Lesbos and all the Greek people which have been so generous in welcoming [migrants]."