Riot police have fired tear gas and stun grenades as thousands of people try to enter Macedonia from Greece.
There were several attempts to charge officers by angry people among a crowd of 3,000 from the Middle East, Africa and Asia.
They had spent the night in the open in a no man's land between the two countries after Macedonia sealed its southern border to migrants and refugees.
At least eight people were injured in the confrontation earlier and one youngster was seen bleeding.
A state of emergency has been declared by Macedonia because of the number of people wanting to head north to Europe, leading to desperate scenes of crowds battling to board packed trains.